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Oracle Deep Internal 4 (ver.2)

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This document discusses transaction slot before-image chaining in Oracle databases. It begins with questions about cleanout, undo storage, and commit SCNs. It then describes the architecture of before-image chaining, where commit SCNs and other metadata are stored in undo blocks and transaction control blocks to link a transaction's multiple before-images together. Diagrams show how before-images are chained across multiple undo blocks using these references.

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© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ver.2 (2016.07.18)
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved.
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ. Transaction slot Before-image Chaining Ⅰ-1. Questions Ⅰ-2. Architecture of transaction slot before-image chaining Ⅰ-3. Flow chart of delayed block cleanout Ⅱ. Block cleanout Analysis Ⅱ-1. Fast block cleanout (Fast commit) Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot Ⅱ-3. Efficient Delayed Block Cleanout (Delayed block cleanout using “commit SCN” of TRN CTL) Ⅱ-4. Inefficient Delayed Block Cleanout (Delayed block cleanout using ”commit SCN” of transaction slot before-image chaining) Table of Agenda
Oracle Deep Internal Ⅰ. Transaction slot Before-image Chaining
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved.
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Select 시 db file sequential read가 반복적으로 수행되는 wait 현상이 대형 오라클 사이트에서 빈번하게 발생 File: Undo file Block: Undo block Ⅰ-1. Questions
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Transaction slot의 commit scn을 data block itl의 scn/fsc 컬럼에 update 하는 것 Cleanout 이란 무엇인가? Question 1 Answer 1 Data blockData block BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------- 0x00 10 0x80 0x04ed 0x0000 0x0000.003dbe4e 0x018000a2 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Transaction 상태 Cleanout 상태 Commit scn Commit scn 적용 전 Commit scn 적용 후 Transaction 상태 Ⅰ-1. Questions
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 순식간에 완료된다. • 일부만 먼저 cleanout 하고 나머지는 나중에 cleanout하기 때문에 시간이 적게 소요된다. 만약 100억 건을 update 한 후에 Commit을 한다면, 100억 건에 대해서 모두 완료하기까지 시간이 얼마나 소요될까? Question 2 Answer 2 Ⅰ-1. Questions
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo는 제한된 자원이기 때문에 트랜잭션 슬롯은 overwrite 된다. 나중에 사용하기 위해서 저장하고 있던 commit SCN은 어떻게 될까? Question 3 • Undo는 제한적인 자원이기 때문에 영원히 보관할 수 없고, 시간이 지나면 aging out 된다. • Undo slot의 before image가 chaining 되면서 저장된다. • (뒤의 슬라이드 참조) Answer 3 Ⅰ-1. Questions Undo Header index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------- 0x00 10 0x80 0x04ed 0x0000 0x0000.003dbe4e 0x018000a2 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Commit scn
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) • Chd: chain header로 링크드 리스트의 시작, 다음 번 트랜잭션이 사용할 트랜잭션 테이블 슬롯 • Ctl: chain tail로 링크드 리스트의 끝, 해당 언두 세그 먼트에서 마지막으로 사용한 트랜잭션 테이블 슬롯 TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 10 0x80 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) Update된 undo header block은 TRN CTL uba에 before-image의 위 치를 기록하고, SCN에 이전 슬롯의 SCN을 기록 2 file#=6 block#=352 Ⅰ-2. Architecture of transaction slot before-image chaining (1/3) chd 0x0006 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x06 slot SCN이 before-image로 저장 1 Before-image Update 2 0x06 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3 1 11 2
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ-2. Architecture of transaction slot before-image chaining (2/3) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba ------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) Before-image UNDO BLK rdba: 0x0180011f seq: 0x485 Rec # 0x2 slt: 0x05 xid: 0x0001.006.00000ad7 uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022c811 prv tx scn: 0x0000.0022c818 rdba: 0x0180011f (6/287) chd 0x0005 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x05 slot SCN이 before-image로 저장 1 1 1 TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011f.0485.02 scn: 0x0000.0022c818 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 10 0x80 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) Update Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록하고, SCN에 이전 슬롯의 SCN을 기록 2 2 2 1 0x05 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ-2. Architecture of transaction slot before-image chaining (3/3) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba ------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) Before-image UNDO BLK rdba: 0x0180011f seq: 0x485 Rec # 0x2 slt: 0x05 xid: 0x0001.006.00000ad7 uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022c811 prv tx scn: 0x0000.0022c818 rdba: 0x0180011f (6/287) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011f.0485.02 scn: 0x0000.0022c818 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x01800120 seq: 0x486 Rec # 0x2 slt: 0x06 xid: 0x0001.005.00000ad5 uba: 0x0180011f.0485.02 ctl max scn: 0x0000.0022c818 prv tx scn: 0x0000.0022c821 rdba: 0x01800120 (6/288) chd 0x0006 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x06 slot SCN이 before-image로 저장 1 1 1 1 TRN CTL seq: 0x0486 chd: 0x0005 ctl: 0x0006 uba: 0x01800120.0486.02 scn: 0x0000.0022c821 index state cflags wrap# uel scn dba -------------------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 10 0x80 0x0ad8 0xffff 0x0000.0022c832 0x01800121 rdba: 0x01800160 (6/352) Update Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록 하고, SCN에 이전 슬롯의 SCN을 기록 2 0x06 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3 2 2 Endless loop..
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. YES NO NO YES YES NO Wrap 번호가 같은가? TRN CTL SCN 적용 Before-image SCN과 비교 반복 수행 해당 SCN 적용 해당 SCN 적용 <Delayed Block cleanout 작업> Efficient delayed block cleanout Inefficient delayed block cleanout delayed block cleanout using “commit SCN” of transaction slot Query SCN이 TRN CTL SCN보다 최신인가? Ⅰ-3. Flow chart of delayed block cleanout Before-image SCN이 Query SCN보다 최신인가?
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. <Inefficient delayed block cleanout> Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 scn: 0x0000.0022d821 index state cflags wrap# uel scn dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022d829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022d832 0x01800121 Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) UNDO BLK: xid: 0x0001.005.00000ad5 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011f.0485.02 ctl max scn: 0x0000.0022d818 prv tx scn: 0x0000.0022d821 txn start scn: scn: 0x0000.0022d831 logon user: 5 prev brb: 25166111 prev bcl: 0 Undo Block buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) *----------------------------- uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022d811 prv tx scn: 0x0000.0022d818 txn start scn: scn: 0x0000.0022d828 logon user: 5 prev brb: 25166110 prev bcl: 0 Wrap 번호 비교 TRN CTL SCN을 Query SCN과 비교 Before image SCN을 Query SCN과 비교 해당 before image SCN으로 적용 0x0ad6 ≠0x0ad8 • Query SCN: 0x0000.0022d811 • Wrap#: 0x0ad6 (itl의 xid) 1 2 3 4 d811 < d821 Query SCN TRN CTL SCN d811 < d818 Query SCN TRN CTL SCN d811 ≥ d811 Query SCN TRN CTL SCN Ⅰ-3. Flow chart of delayed block cleanout NO NO NO Wrap 번호가 같은가? 해당 SCN 적용 Query SCN이 TRN CTL SCN보다 최신인가? Before-image SCN이 Query SCN보다 최신인가? 2 3 1 4
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ. Transaction slot Before-image Chaining Ⅰ-1. Questions Ⅰ-2. Architecture of transaction slot before-image chaining Ⅰ-3. Flow chart of delayed block cleanout Ⅱ. Block cleanout Analysis Ⅱ-1. Fast block cleanout (Fast commit) Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot Ⅱ-3. Efficient Delayed Block Cleanout (Delayed block cleanout using “commit SCN” of TRN CTL) Ⅱ-4. Inefficient Delayed Block Cleanout (Delayed block cleanout using ”commit SCN” of transaction slot before-image chaining) Table of Agenda
Oracle Deep Internal Ⅱ. Block cleanout Analysis
Oracle Deep Internal Ⅱ-1. Fast block cleanout (Fast commit)
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Commit SCN ↓ 9 (Committed) 10 (Active) 0x01 0x0008.013. 000018a8 1--U- Commit SCN (Base#) 0x13 0x008004f8 0x008004f8. 00cf.06 버퍼 캐시의 10% 초과하지 않는 블록들은 세션 메모리 내에 리스트로 생성 Fast block cleanout은 “트랜잭션이 종료되는 시점에 Dirty블록에 관련된 트랜잭션의 정보를 정리하는 작업” 0x18a8 Ⅱ-1. Fast block cleanout (Fast commit)
Oracle Deep Internal Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Delayed block cleanout은 “커밋 시점에 클린아웃 되지 않은 블록들(변경하려는 블록의 수가 버퍼 캐시의 10%를 초과), 메모리에서 flush되어 cleanout 처리되지 않고 datafile에 기록된 블록들을 다음 세션에 의해 클린아웃 작업” 0x13 0x0080006c 0x01 0C--- Commit SCN0x008004f8 00cf.06 9 (Committed) Commit SCN0x18a8 0x0008.013. 000018a8 Row Lock 클린아웃 되지 않은 트랜잭션의 xid를 이용해 transaction table을 확인(트랜잭션 종료여부, SCN)후, 해당 ITL에 Lock byte 해제, SCN 설정, Flag를 C---로 변경 후 이에 대한 redo log를 생성한다. Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot
Oracle Deep Internal Ⅱ-3. Efficient Delayed Block Cleanout
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Upper bound commit은 “원래 commit이 일어난 시점의 SCN이어야 하지만 다른 트랜잭션에 의해 overwrite 되었을 경우, cleanout 할 쿼리 SCN(818)부터 시작해서 원래 commit이 일어난 시점의 SCN(811) 사이에 있는 가장 높은 값(817)을 의미한다” Upper bound commit Upper bound commit
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. • Undo segment 10개 중 9개 offline, 1개만 online • Undo segment의 34개 슬롯 중 32개 active, 2개만 사용 가능 시나리오 Update Table T1 Flush Buffer Commit Update & Commit Update & Commit Update & Commit Update & Commit Select Table T1 t1 t2 t3 S1 S2Time Ⅱ-3. Efficient Delayed Block Cleanout
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows 1. 초기상태 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Block ASCII HEXA code 41 => Value ‘A’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows ITL Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Header를 메모리에 적재 Undo Block ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 chd 0x0014 슬롯을 사용할 예정이기 때문에 uba, TRN CTL SCN, 0x14 slot SCN이 before-image로 저장 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록, SCN에 이전 슬롯의 SCN을 기록 0x14 슬롯 갱신 (state, cflag, wrap#, scn) Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ Before image가 있는 Undo Block 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 3. alter system flush buffer_cache ; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 flush ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 4. commit; BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0x0014 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353b 0xffff 0x0000.006e8efd 0x0180011b Undo Header Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 5. Undo Header Slot 재사용 (세션2에서 Update 첫 번째) BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0014 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.32 scn: 0x0000.006e8ee4 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 10 0x80 0x3539 0x0005 0x0000.006e8f05 0x0180011d 0x14 9 0x00 0x353b 0xffff 0x0000.006e8efd 0x0180011b ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Session2> Update t2 set col2=‘B’; Session2> Commit; Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Block buffer tsn: 6 rdba: 0x0180011d (6/285) UNDO BLK: xid: 0x0006.004.00003539 seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x04 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 41 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Header BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011d.1cc1.02 scn: 0x0000.006e8efd … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3539 0xffff 0x0000.006e8f06 0x0180011d 0x14 10 0x80 0x353c 0x0005 0x0000.006e8f0d 0x0180011e buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b 6. Undo Header Slot 재사용 (세션2에서 Update 두 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Block buffer tsn: 6 rdba: 0x0180011e (6/286) UNDO BLK: xid: 0x0006.014.0000353c seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 50 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block Undo Header BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0014 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.1cc1.02 scn: 0x0000.006e8f06 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 10 0x80 0x353a 0x0005 0x0000.006e8f15 0x0180011f 0x14 9 0x00 0x353c 0xffff 0x0000.006e8f0e 0x0180011e buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0006.004.0000353a seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x04 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 51 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Session2> Update t2 set col2=‘B’; Session2> Commit; 7. Undo Header Slot 재사용 (세션2에서 Update 세 번째) ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 3 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0xffff 0x0000.006e8f16 0x0180011f 0x14 10 0x80 0x353d 0x0005 0x0000.006e8f1c 0x01800130 Query SCN 8. Undo Header Slot 재사용 (세션2에서 Update 네 번째) Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Session2> Update t2 set col2=‘B’; Session2> Commit;
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x647efe78) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x646aa000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 9. select /*+ full(t1) */count(*) from t1 where rownum <= 1; 현재 시점 undo header block 의 TRN CTL SCN 값으로 cleanout. BH (0x657f85c0) file#: 5 rdba: 0x01418413 (5/99347) class: 1 ba: 0x65788000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x01418413 (5/99347) … 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Itl Xid Uba Flag Lck Scn/fsc Wrap number가 다름 Query SCN은 0x0000.006e8f1c ASCII HEXA code 42 => Value ‘B’ ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Begin cleaning out block ... Block header dump: 0x01418413 … Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #139971596639184: nam='db file sequential read' ela= 15 file#=6 block#=288 blocks=1 obj#=0 tim=1460423039184663 … Block cleanout record, scn: 0xffff.ffffffff ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 scn: 0x0000.006e8f0e Block header dump: 0x01418413 … Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x647efe78) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x646aa000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 9. select /*+ full(t1) */count(*) from t1 where rownum <= 1; 현재 시점 undo header block 의 TRN CTL SCN 값으로 cleanout. BH (0x657f85c0) file#: 5 rdba: 0x01418413 (5/99347) class: 1 ba: 0x65788000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x01418413 (5/99347) … 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Itl Xid Uba Flag Lck Scn/fsc Wrap number가 다름 Query SCN은 0x0000.006e8f1c ASCII HEXA code 42 => Value ‘B’ ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
Oracle Deep Internal Ⅱ-4. Inefficient Delayed Block Cleanout
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Update Table T1 Flush Buffer Commit Select Table T1 t1 t2 t4 S1 S2Time t3 Update & Commit Update & Commit Update & Commit Update & Commit Set transaction read only Ⅱ-4. Inefficient delayed block cleanout • Undo segment 10개 중 9개 offline, 1개만 online • Undo segment의 34개 슬롯 중 32개 active, 2개만 사용 가능 시나리오
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows 1. 초기상태 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Block ASCII HEXA code 41 => Value ‘A’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows ITL Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Header를 메모리에 적재 Undo Block ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 chd 0x0006 슬롯을 사용할 예정이기 때 문에 uba, TRN CTL SCN, 0x06 slot SCN이 before-mage로 저장 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록, SCN에 이전 슬롯의 SCN을 기록 0x06 슬롯 갱신 (state, cflag, wrap#, SCN) Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ Before-image가 있는 Undo Block 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Rows ITL Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B'; block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 3. alter system flush buffer_cache ; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 flush ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 4. commit; BH (0x66be9f68) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66a0e000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0x0006 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad6 0xffff 0x0000.0022c811 0x0180011c Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Query SCN
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 5. Set transaction read only ; Undo Header Undo Block <Read only 시점> • 현재 세션 Commit 시점 이후 (0x0000.0022c811) • 다른 세션 Commit 시점 이전 (0x0000.0022c818) ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 6. Undo Header Slot 재사용 (세션2에서 Update 첫 번째) Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.31 SCN: 0x0000.0022c7ff index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.005.00000ad4 seq: 0x485 cnt: 0x32 irb: 0x32 icl: 0x0 flg: 0x0000 * Rec #0x31 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011c.0485.09 ctl max SCN: 0x0000.0022c7fe prv tx SCN: 0x0000.0022c7ff txn start SCN: SCN: 0x0000.0022c816 logon user: 5 prev brb: 25166109 prev bcl: 0 Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 7. Undo Header Slot 재사용 (세션2에서 Update 두 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f buffer tsn: 6 rdba: 0x0180011e (6/286) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x3 irb: 0x3 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011c.0485.31 ctl max SCN: 0x0000.0022c7ff prv tx SCN: 0x0000.0022c811 txn start SCN: SCN: 0x0000.0022c820 logon user: 5 prev brb: 25166108 prev bcl: 0
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 8. Undo Header Slot 재사용 (세션2에서 Update 세 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.0485.02 SCN: 0x0000.0022c818 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011e.0485.02 ctl max SCN: 0x0000.0022c811 prv tx SCN: 0x0000.0022c818 txn start SCN: SCN: 0x0000.0022c828 logon user: 5 prev brb: 25166110 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 9. Undo Header Slot 재사용 (세션2에서 Update 네 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800120 (6/288) UNDO BLK: xid: 0x0001.005.00000ad5 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011f.0485.02 ctl max SCN: 0x0000.0022c818 prv tx SCN: 0x0000.0022c821 txn start SCN: SCN: 0x0000.0022c831 logon user: 5 prev brb: 25166111 prev bcl: 0
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc BH (0x673f4b40) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x67328000 st: CR md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) Begin cleaning out block ... Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #140004262172792: nam='db file sequential read' ela= 9 file#=6 block#=352 blocks=1 obj#=0 tim=1459261058673224 WAIT #140004262172792: nam='db file sequential read' ela= 13 file#=6 block#=288 blocks=1 obj#=0 tim=1459261058676417 WAIT #140004262172792: nam='db file sequential read' ela= 10 file#=6 block#=287 blocks=1 obj#=0 tim=1459261058677687 … Block cleanout record, SCN: 0x0000.0022c834 ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 SCN: 0x0000.0022c811 Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block 두 번째 update Undo Block 첫 번째 update Undo Block
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) Query SCN은 0x0000.0022c811 Wrap number가 다름 Begin cleaning out block ... Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #140004262172792: nam='db file sequential read' ela= 9 file#=6 block#=352 blocks=1 obj#=0 tim=1459261058673224 WAIT #140004262172792: nam='db file sequential read' ela= 13 file#=6 block#=288 blocks=1 obj#=0 tim=1459261058676417 WAIT #140004262172792: nam='db file sequential read' ela= 10 file#=6 block#=287 blocks=1 obj#=0 tim=1459261058677687 … Block cleanout record, SCN: 0x0000.0022c834 ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 SCN: 0x0000.0022c811 Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block 두 번째 update Undo Block 첫 번째 update Undo Block SCN: 0x0000.0022c821 SCN: 0x0000.0022c818 SCN: 0x0000.0022c811
SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) 1 BH (0x673f4b40) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x67328000 st: CR md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f CR 블록 적용
© Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Oracle Deep Internal Blog Video E-mail NAVER http://cafe.naver.com/playexem ITPUB http://blog.itpub.net/31135309/ Wordpress https://playexem.wordpress.com/ Slideshare http://www.slideshare.net/playexem Youtube https://www.youtube.com/channel/UC5wKR_ -A0eL_Pn_EMzoauJg Tudou http://www.tudou.com/home/maxgauge/ 교육 문의 : 연구컨텐츠팀 김숙진 edu@ex-em.com

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Oracle Deep Internal 4 (ver.2)

  • 1. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ver.2 (2016.07.18)
  • 2. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved.
  • 3. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ. Transaction slot Before-image Chaining Ⅰ-1. Questions Ⅰ-2. Architecture of transaction slot before-image chaining Ⅰ-3. Flow chart of delayed block cleanout Ⅱ. Block cleanout Analysis Ⅱ-1. Fast block cleanout (Fast commit) Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot Ⅱ-3. Efficient Delayed Block Cleanout (Delayed block cleanout using “commit SCN” of TRN CTL) Ⅱ-4. Inefficient Delayed Block Cleanout (Delayed block cleanout using ”commit SCN” of transaction slot before-image chaining) Table of Agenda
  • 4. Oracle Deep Internal Ⅰ. Transaction slot Before-image Chaining
  • 5. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved.
  • 6. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Select 시 db file sequential read가 반복적으로 수행되는 wait 현상이 대형 오라클 사이트에서 빈번하게 발생 File: Undo file Block: Undo block Ⅰ-1. Questions
  • 7. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Transaction slot의 commit scn을 data block itl의 scn/fsc 컬럼에 update 하는 것 Cleanout 이란 무엇인가? Question 1 Answer 1 Data blockData block BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 ---- 1 fsc 0x0000.00000000 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 BH (0x643fa1c8) file#: 5 rdba: 0x0140dcad (5/56493) class: 1 ba: 0x643b6000 st: XCURRENT md: EXCL fpin: 'kdswh11: kdst_fetch' tch: 1 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x000a.000.00000534 0x018000d2.01e6.01 C--- 0 scn 0x0000.003dbe3a 0x02 0x0007.000.000004ed 0x018000a2.01d5.01 --U- 1 fsc 0x0000.003dbe4e tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------- 0x00 10 0x80 0x04ed 0x0000 0x0000.003dbe4e 0x018000a2 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Transaction 상태 Cleanout 상태 Commit scn Commit scn 적용 전 Commit scn 적용 후 Transaction 상태 Ⅰ-1. Questions
  • 8. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 순식간에 완료된다. • 일부만 먼저 cleanout 하고 나머지는 나중에 cleanout하기 때문에 시간이 적게 소요된다. 만약 100억 건을 update 한 후에 Commit을 한다면, 100억 건에 대해서 모두 완료하기까지 시간이 얼마나 소요될까? Question 2 Answer 2 Ⅰ-1. Questions
  • 9. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo는 제한된 자원이기 때문에 트랜잭션 슬롯은 overwrite 된다. 나중에 사용하기 위해서 저장하고 있던 commit SCN은 어떻게 될까? Question 3 • Undo는 제한적인 자원이기 때문에 영원히 보관할 수 없고, 시간이 지나면 aging out 된다. • Undo slot의 before image가 chaining 되면서 저장된다. • (뒤의 슬라이드 참조) Answer 3 Ⅰ-1. Questions Undo Header index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------- 0x00 10 0x80 0x04ed 0x0000 0x0000.003dbe4e 0x018000a2 0x01 9 0x00 0x04ec 0x0002 0x0000.003d6d72 0x00000000 0x02 9 0x00 0x04ec 0x0003 0x0000.003d6d72 0x00000000 Commit scn
  • 10. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) • Chd: chain header로 링크드 리스트의 시작, 다음 번 트랜잭션이 사용할 트랜잭션 테이블 슬롯 • Ctl: chain tail로 링크드 리스트의 끝, 해당 언두 세그 먼트에서 마지막으로 사용한 트랜잭션 테이블 슬롯 TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 10 0x80 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) Update된 undo header block은 TRN CTL uba에 before-image의 위 치를 기록하고, SCN에 이전 슬롯의 SCN을 기록 2 file#=6 block#=352 Ⅰ-2. Architecture of transaction slot before-image chaining (1/3) chd 0x0006 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x06 slot SCN이 before-image로 저장 1 Before-image Update 2 0x06 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3 1 11 2
  • 11. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ-2. Architecture of transaction slot before-image chaining (2/3) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba ------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) Before-image UNDO BLK rdba: 0x0180011f seq: 0x485 Rec # 0x2 slt: 0x05 xid: 0x0001.006.00000ad7 uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022c811 prv tx scn: 0x0000.0022c818 rdba: 0x0180011f (6/287) chd 0x0005 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x05 slot SCN이 before-image로 저장 1 1 1 TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011f.0485.02 scn: 0x0000.0022c818 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 10 0x80 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) Update Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록하고, SCN에 이전 슬롯의 SCN을 기록 2 2 2 1 0x05 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3
  • 12. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ-2. Architecture of transaction slot before-image chaining (3/3) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011c.0485.31 scn: 0x0000.0022c7ff index state cflags wrap# uel scn dba ------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c rdba: 0x01800160 (6/352) TRN CTL seq: 0x0485 chd: 0x0005 ctl: 0x0006 uba: 0x0180011e.0485.02 scn: 0x0000.0022c811 index state cflags wrap# uel scn dba ------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x0180011e seq: 0x485 Rec # 0x2 slt: 0x06 xid: 0x0001.006.00000ad7 uba: 0x0180011c.0485.31 ctl max scn: 0x0000.0022c7ff prv tx scn: 0x0000.0022c811 rdba: 0x0180011e (6/286) Before-image UNDO BLK rdba: 0x0180011f seq: 0x485 Rec # 0x2 slt: 0x05 xid: 0x0001.006.00000ad7 uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022c811 prv tx scn: 0x0000.0022c818 rdba: 0x0180011f (6/287) TRN CTL seq: 0x0485 chd: 0x0006 ctl: 0x0005 uba: 0x0180011f.0485.02 scn: 0x0000.0022c818 index state cflags wrap# uel scn dba --------------------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f rdba: 0x01800160 (6/352) UNDO BLK rdba: 0x01800120 seq: 0x486 Rec # 0x2 slt: 0x06 xid: 0x0001.005.00000ad5 uba: 0x0180011f.0485.02 ctl max scn: 0x0000.0022c818 prv tx scn: 0x0000.0022c821 rdba: 0x01800120 (6/288) chd 0x0006 슬롯을 사용할 예정이기 때문에 uba, trn ctl SCN, 0x06 slot SCN이 before-image로 저장 1 1 1 1 TRN CTL seq: 0x0486 chd: 0x0005 ctl: 0x0006 uba: 0x01800120.0486.02 scn: 0x0000.0022c821 index state cflags wrap# uel scn dba -------------------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 10 0x80 0x0ad8 0xffff 0x0000.0022c832 0x01800121 rdba: 0x01800160 (6/352) Update Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록 하고, SCN에 이전 슬롯의 SCN을 기록 2 0x06 슬롯 갱신 (state 10, cflags 0x80, SCN 갱신) 3 2 2 Endless loop..
  • 13. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. YES NO NO YES YES NO Wrap 번호가 같은가? TRN CTL SCN 적용 Before-image SCN과 비교 반복 수행 해당 SCN 적용 해당 SCN 적용 <Delayed Block cleanout 작업> Efficient delayed block cleanout Inefficient delayed block cleanout delayed block cleanout using “commit SCN” of transaction slot Query SCN이 TRN CTL SCN보다 최신인가? Ⅰ-3. Flow chart of delayed block cleanout Before-image SCN이 Query SCN보다 최신인가?
  • 14. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. <Inefficient delayed block cleanout> Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 scn: 0x0000.0022d821 index state cflags wrap# uel scn dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022d829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022d832 0x01800121 Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) UNDO BLK: xid: 0x0001.005.00000ad5 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011f.0485.02 ctl max scn: 0x0000.0022d818 prv tx scn: 0x0000.0022d821 txn start scn: scn: 0x0000.0022d831 logon user: 5 prev brb: 25166111 prev bcl: 0 Undo Block buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) *----------------------------- uba: 0x0180011e.0485.02 ctl max scn: 0x0000.0022d811 prv tx scn: 0x0000.0022d818 txn start scn: scn: 0x0000.0022d828 logon user: 5 prev brb: 25166110 prev bcl: 0 Wrap 번호 비교 TRN CTL SCN을 Query SCN과 비교 Before image SCN을 Query SCN과 비교 해당 before image SCN으로 적용 0x0ad6 ≠0x0ad8 • Query SCN: 0x0000.0022d811 • Wrap#: 0x0ad6 (itl의 xid) 1 2 3 4 d811 < d821 Query SCN TRN CTL SCN d811 < d818 Query SCN TRN CTL SCN d811 ≥ d811 Query SCN TRN CTL SCN Ⅰ-3. Flow chart of delayed block cleanout NO NO NO Wrap 번호가 같은가? 해당 SCN 적용 Query SCN이 TRN CTL SCN보다 최신인가? Before-image SCN이 Query SCN보다 최신인가? 2 3 1 4
  • 15. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Ⅰ. Transaction slot Before-image Chaining Ⅰ-1. Questions Ⅰ-2. Architecture of transaction slot before-image chaining Ⅰ-3. Flow chart of delayed block cleanout Ⅱ. Block cleanout Analysis Ⅱ-1. Fast block cleanout (Fast commit) Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot Ⅱ-3. Efficient Delayed Block Cleanout (Delayed block cleanout using “commit SCN” of TRN CTL) Ⅱ-4. Inefficient Delayed Block Cleanout (Delayed block cleanout using ”commit SCN” of transaction slot before-image chaining) Table of Agenda
  • 16. Oracle Deep Internal Ⅱ. Block cleanout Analysis
  • 17. Oracle Deep Internal Ⅱ-1. Fast block cleanout (Fast commit)
  • 18. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Commit SCN ↓ 9 (Committed) 10 (Active) 0x01 0x0008.013. 000018a8 1--U- Commit SCN (Base#) 0x13 0x008004f8 0x008004f8. 00cf.06 버퍼 캐시의 10% 초과하지 않는 블록들은 세션 메모리 내에 리스트로 생성 Fast block cleanout은 “트랜잭션이 종료되는 시점에 Dirty블록에 관련된 트랜잭션의 정보를 정리하는 작업” 0x18a8 Ⅱ-1. Fast block cleanout (Fast commit)
  • 19. Oracle Deep Internal Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot
  • 20. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Delayed block cleanout은 “커밋 시점에 클린아웃 되지 않은 블록들(변경하려는 블록의 수가 버퍼 캐시의 10%를 초과), 메모리에서 flush되어 cleanout 처리되지 않고 datafile에 기록된 블록들을 다음 세션에 의해 클린아웃 작업” 0x13 0x0080006c 0x01 0C--- Commit SCN0x008004f8 00cf.06 9 (Committed) Commit SCN0x18a8 0x0008.013. 000018a8 Row Lock 클린아웃 되지 않은 트랜잭션의 xid를 이용해 transaction table을 확인(트랜잭션 종료여부, SCN)후, 해당 ITL에 Lock byte 해제, SCN 설정, Flag를 C---로 변경 후 이에 대한 redo log를 생성한다. Ⅱ-2. Delayed block cleanout using “commit SCN” of transaction slot
  • 21. Oracle Deep Internal Ⅱ-3. Efficient Delayed Block Cleanout
  • 22. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Upper bound commit은 “원래 commit이 일어난 시점의 SCN이어야 하지만 다른 트랜잭션에 의해 overwrite 되었을 경우, cleanout 할 쿼리 SCN(818)부터 시작해서 원래 commit이 일어난 시점의 SCN(811) 사이에 있는 가장 높은 값(817)을 의미한다” Upper bound commit Upper bound commit
  • 23. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. • Undo segment 10개 중 9개 offline, 1개만 online • Undo segment의 34개 슬롯 중 32개 active, 2개만 사용 가능 시나리오 Update Table T1 Flush Buffer Commit Update & Commit Update & Commit Update & Commit Update & Commit Select Table T1 t1 t2 t3 S1 S2Time Ⅱ-3. Efficient Delayed Block Cleanout
  • 24. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows 1. 초기상태 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Block ASCII HEXA code 41 => Value ‘A’
  • 25. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows ITL Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Header를 메모리에 적재 Undo Block ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 26. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 chd 0x0014 슬롯을 사용할 예정이기 때문에 uba, TRN CTL SCN, 0x14 slot SCN이 before-image로 저장 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 27. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록, SCN에 이전 슬롯의 SCN을 기록 0x14 슬롯 갱신 (state, cflag, wrap#, scn) Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ Before image가 있는 Undo Block 2. update t1 set col2='B';
  • 28. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 29. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x63fe3de8) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63d6e000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0004 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.1cc1.05 scn: 0x0000.006e8ee1 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353a 0x0004 0x0000.006e8ee3 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 30. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 3. alter system flush buffer_cache ; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 flush ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 31. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 4. commit; BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0x0014 0x0000.006e8ee4 0x0180011b 0x14 9 0x00 0x353b 0xffff 0x0000.006e8efd 0x0180011b Undo Header Undo Block buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011b (6/283) UNDO BLK: xid: 0x0006.014.0000353b seq: 0x1cc1 cnt: 0x31 irb: 0x31 icl: 0x0 flg: 0x0000 * Rec #0xa slt: 0x14 objn: 78003(0x000130b3) objd: 78003 tblspc: 5(0x00000005) uba: 0x0180011c.1cc1.05 ctl max scn: 0x0000.006e8ee1 prv tx scn: 0x0000.006e8ee3 txn start scn: scn: 0x0000.006e8efa logon user: 5 prev brb: 25166108 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 32. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 5. Undo Header Slot 재사용 (세션2에서 Update 첫 번째) BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0014 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.32 scn: 0x0000.006e8ee4 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 10 0x80 0x3539 0x0005 0x0000.006e8f05 0x0180011d 0x14 9 0x00 0x353b 0xffff 0x0000.006e8efd 0x0180011b ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Session2> Update t2 set col2=‘B’; Session2> Commit; Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b Undo Block buffer tsn: 6 rdba: 0x0180011d (6/285) UNDO BLK: xid: 0x0006.004.00003539 seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x04 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 41 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
  • 33. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Header BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011d.1cc1.02 scn: 0x0000.006e8efd … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3539 0xffff 0x0000.006e8f06 0x0180011d 0x14 10 0x80 0x353c 0x0005 0x0000.006e8f0d 0x0180011e buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b 6. Undo Header Slot 재사용 (세션2에서 Update 두 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Block buffer tsn: 6 rdba: 0x0180011e (6/286) UNDO BLK: xid: 0x0006.014.0000353c seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 50 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20
  • 34. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block Undo Header BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 2 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc1 chd: 0x0014 ctl: 0x0014 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.1cc1.02 scn: 0x0000.006e8f06 … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 10 0x80 0x353a 0x0005 0x0000.006e8f15 0x0180011f 0x14 9 0x00 0x353c 0xffff 0x0000.006e8f0e 0x0180011e buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0006.004.0000353a seq: 0x1cc1 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x04 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 51 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Session2> Update t2 set col2=‘B’; Session2> Commit; 7. Undo Header Slot 재사용 (세션2에서 Update 세 번째) ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 35. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x637f5020) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x63730000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 3 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0xffff 0x0000.006e8f16 0x0180011f 0x14 10 0x80 0x353d 0x0005 0x0000.006e8f1c 0x01800130 Query SCN 8. Undo Header Slot 재사용 (세션2에서 Update 네 번째) Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc1 chd: 0x0004 ctl: 0x0004 inc: 0x00000000 nfb: 0x0000 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011b.1cc1.0a scn: 0x0000.006e8ee3 index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x3538 0xffff 0x0000.006e8ee4 0x0180011b 0x14 10 0x80 0x353b 0x0005 0x0000.006e8efa 0x0180011b buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Session2> Update t2 set col2=‘B’; Session2> Commit;
  • 36. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x647efe78) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x646aa000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 9. select /*+ full(t1) */count(*) from t1 where rownum <= 1; 현재 시점 undo header block 의 TRN CTL SCN 값으로 cleanout. BH (0x657f85c0) file#: 5 rdba: 0x01418413 (5/99347) class: 1 ba: 0x65788000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x01418413 (5/99347) … 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Itl Xid Uba Flag Lck Scn/fsc Wrap number가 다름 Query SCN은 0x0000.006e8f1c ASCII HEXA code 42 => Value ‘B’ ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Begin cleaning out block ... Block header dump: 0x01418413 … Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #139971596639184: nam='db file sequential read' ela= 15 file#=6 block#=288 blocks=1 obj#=0 tim=1460423039184663 … Block cleanout record, scn: 0xffff.ffffffff ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 scn: 0x0000.006e8f0e Block header dump: 0x01418413 … Itl Xid Uba Flag Lck Scn/Fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block
  • 37. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x647efe78) file#: 6 rdba: 0x01800120 (6/288) class: 27 ba: 0x646aa000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 1 buffer tsn: 6 rdba: 0x01800120 (6/288) … TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e … index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 9. select /*+ full(t1) */count(*) from t1 where rownum <= 1; 현재 시점 undo header block 의 TRN CTL SCN 값으로 cleanout. BH (0x657f85c0) file#: 5 rdba: 0x01418413 (5/99347) class: 1 ba: 0x65788000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x01418413 (5/99347) … 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 C-U- 0 scn 0x0000.006e8f0e 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Block Undo Header buffer tsn: 6 rdba: 0x01800120 (6/288) TRN CTL:: seq: 0x1cc2 chd: 0x0004 ctl: 0x0014 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.1cc1.02 scn: 0x0000.006e8f0e index state cflags wrap# uel scn dba ----------------------------------------------------------------------------------------- 0x04 9 0x00 0x353a 0x0014 0x0000.006e8f16 0x0180011f 0x14 9 0x00 0x353d 0xffff 0x0000.006e8f1e 0x01800130 buffer tsn: 6 rdba: 0x01800130 (6/304) UNDO BLK: xid: 0x0006.014.0000353d seq: 0x1cc2 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x14 objn: 78004(0x000130b4) objd: 78004 tblspc: 5(0x00000005) col 1: [2000] 52 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 Itl Xid Uba Flag Lck Scn/fsc Wrap number가 다름 Query SCN은 0x0000.006e8f1c ASCII HEXA code 42 => Value ‘B’ ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x002c.002.000000b4 0x00000000.0000.00 C--- 0 scn 0x0000.006e8426 0x02 0x0006.014.0000353b 0x0180011b.1cc1.28 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 38. Oracle Deep Internal Ⅱ-4. Inefficient Delayed Block Cleanout
  • 39. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Update Table T1 Flush Buffer Commit Select Table T1 t1 t2 t4 S1 S2Time t3 Update & Commit Update & Commit Update & Commit Update & Commit Set transaction read only Ⅱ-4. Inefficient delayed block cleanout • Undo segment 10개 중 9개 offline, 1개만 online • Undo segment의 34개 슬롯 중 32개 active, 2개만 사용 가능 시나리오
  • 40. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows 1. 초기상태 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Block ASCII HEXA code 41 => Value ‘A’
  • 41. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Rows ITL Undo Header block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Header를 메모리에 적재 Undo Block ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 42. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 chd 0x0006 슬롯을 사용할 예정이기 때 문에 uba, TRN CTL SCN, 0x06 slot SCN이 before-mage로 저장 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 43. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Update된 undo header block은 TRN CTL uba에 before-image의 위치를 기록, SCN에 이전 슬롯의 SCN을 기록 0x06 슬롯 갱신 (state, cflag, wrap#, SCN) Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ Before-image가 있는 Undo Block 2. update t1 set col2='B';
  • 44. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B';
  • 45. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Undo Block buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 BH (0x663ea0a0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66210000 st: XCURRENT md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c Undo Header buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.05 SCN: 0x0000.0022c7fb index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad5 0x0005 0x0000.0022c7fe 0x0180011c Rows ITL Rows ITL block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 41 => Value ‘A’ 2. update t1 set col2='B'; block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 41 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001e.01b.0000000d 0x00000000.0000.00 C--- 0 SCN 0x0000.002263d9 0x02 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 ASCII HEXA code 42 => Value ‘B’
  • 46. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 3. alter system flush buffer_cache ; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 flush ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 47. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 4. commit; BH (0x66be9f68) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x66a0e000 st: XCURRENT md: NULL fpin: 'ktuwh61: ktugus:ktucmt' tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad3 0x0006 0x0000.0022c7ff 0x0180011d 0x06 9 0x00 0x0ad6 0xffff 0x0000.0022c811 0x0180011c Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Query SCN
  • 48. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 5. Set transaction read only ; Undo Header Undo Block <Read only 시점> • 현재 세션 Commit 시점 이후 (0x0000.0022c811) • 다른 세션 Commit 시점 이전 (0x0000.0022c818) ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0005 inc: 0x00000000 nfb: 0x0001 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.09 SCN: 0x0000.0022c7fe index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad3 0xffff 0x0000.0022c7ff 0x0180011d 0x06 10 0x80 0x0ad6 0x0005 0x0000.0022c809 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.006.00000ad6 seq: 0x485 cnt: 0x30 irb: 0x30 icl: 0x0 flg: 0x0000 * Rec #0x9 slt: 0x06 objn: 70145(0x00011201) objd: 70145 tblspc: 5(0x00000005) uba: 0x0180011c.0485.05 ctl max SCN: 0x0000.0022c7fb prv tx SCN: 0x0000.0022c7fe txn start SCN: SCN: 0x0000.0022c809 logon user: 5 prev brb: 25166108 prev bcl: 0
  • 49. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 6. Undo Header Slot 재사용 (세션2에서 Update 첫 번째) Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011c.0485.31 SCN: 0x0000.0022c7ff index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad4 0xffff 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad6 0x0005 0x0000.0022c811 0x0180011c buffer tsn: 6 rdba: 0x0180011c (6/284) UNDO BLK: xid: 0x0001.005.00000ad4 seq: 0x485 cnt: 0x32 irb: 0x32 icl: 0x0 flg: 0x0000 * Rec #0x31 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011c.0485.09 ctl max SCN: 0x0000.0022c7fe prv tx SCN: 0x0000.0022c7ff txn start SCN: SCN: 0x0000.0022c816 logon user: 5 prev brb: 25166109 prev bcl: 0 Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 50. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 7. Undo Header Slot 재사용 (세션2에서 Update 두 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0485 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f buffer tsn: 6 rdba: 0x0180011e (6/286) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x3 irb: 0x3 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011c.0485.31 ctl max SCN: 0x0000.0022c7ff prv tx SCN: 0x0000.0022c811 txn start SCN: SCN: 0x0000.0022c820 logon user: 5 prev brb: 25166108 prev bcl: 0
  • 51. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 8. Undo Header Slot 재사용 (세션2에서 Update 세 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0006 ctl: 0x0005 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011f.0485.02 SCN: 0x0000.0022c818 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0xffff 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad7 0x0005 0x0000.0022c821 0x0180011f buffer tsn: 6 rdba: 0x0180011f (6/287) UNDO BLK: xid: 0x0001.006.00000ad7 seq: 0x485 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x05 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011e.0485.02 ctl max SCN: 0x0000.0022c811 prv tx SCN: 0x0000.0022c818 txn start SCN: SCN: 0x0000.0022c828 logon user: 5 prev brb: 25166110 prev bcl: 0 ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’
  • 52. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. 9. Undo Header Slot 재사용 (세션2에서 Update 네 번째) Session2> Update t2 set col2=‘B’; Session2> Commit; ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 ASCII HEXA code 42 => Value ‘B’ Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800120 (6/288) UNDO BLK: xid: 0x0001.005.00000ad5 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x2 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) uba: 0x0180011f.0485.02 ctl max SCN: 0x0000.0022c818 prv tx SCN: 0x0000.0022c821 txn start SCN: SCN: 0x0000.0022c831 logon user: 5 prev brb: 25166111 prev bcl: 0
  • 53. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc BH (0x673f4b40) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x67328000 st: CR md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) Begin cleaning out block ... Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #140004262172792: nam='db file sequential read' ela= 9 file#=6 block#=352 blocks=1 obj#=0 tim=1459261058673224 WAIT #140004262172792: nam='db file sequential read' ela= 13 file#=6 block#=288 blocks=1 obj#=0 tim=1459261058676417 WAIT #140004262172792: nam='db file sequential read' ela= 10 file#=6 block#=287 blocks=1 obj#=0 tim=1459261058677687 … Block cleanout record, SCN: 0x0000.0022c834 ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 SCN: 0x0000.0022c811 Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block 두 번째 update Undo Block 첫 번째 update Undo Block
  • 54. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) Query SCN은 0x0000.0022c811 Wrap number가 다름 Begin cleaning out block ... Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 WAIT #140004262172792: nam='db file sequential read' ela= 9 file#=6 block#=352 blocks=1 obj#=0 tim=1459261058673224 WAIT #140004262172792: nam='db file sequential read' ela= 13 file#=6 block#=288 blocks=1 obj#=0 tim=1459261058676417 WAIT #140004262172792: nam='db file sequential read' ela= 10 file#=6 block#=287 blocks=1 obj#=0 tim=1459261058677687 … Block cleanout record, SCN: 0x0000.0022c834 ver: 0x01 opt: 0x01, entries follow... itli: 2 flg: 1 SCN: 0x0000.0022c811 Block header dump: 0x014000e3 … Itl Xid Uba Flag Lck SCN/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Undo header Block 두 번째 update Undo Block 첫 번째 update Undo Block SCN: 0x0000.0022c821 SCN: 0x0000.0022c818 SCN: 0x0000.0022c811
  • 55. SGA Undo SegmentData Block © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. BH (0x623e85d0) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x621e4000 st: XCURRENT md: NULL fpin: 'ktuwh05: ktugct' tch: 0 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------- 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 10. select /*+ full(t1) */count(*) from t1 where rownum <= 1; undo header block 의 CR을 만드는 과정에서 undo block read 발생함. BH (0x66bf7720) file#: 5 rdba: 0x014000e3 (5/227) class: 1 ba: 0x66b70000 st: XCURRENT md: NULL fpin: 'kdswh11: kdst_fetch' tch: 1 buffer tsn: 5 rdba: 0x014000e3 (5/227) … 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 C-U- 0 SCN 0x0000.0022c811 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 … block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x0 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Itl Xid Uba Flag Lck SCN/fsc ITL Itl Xid Uba Flag Lck Scn/fsc 0x01 0x001c.005.00000010 0x00000000.0000.00 C--- 0 SCN 0x0000.0022bf23 0x02 0x0001.006.00000ad6 0x0180011c.0485.27 ---- 3 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 Rows block_row_dump: tab 0, row 0, @0x1f70 tl: 16 fb: --H-FL-- lb: 0x2 cc: 2 col 0: [10] 31 20 20 20 20 20 20 20 20 20 col 1: [ 1] 42 Undo Header Undo Block buffer tsn: 6 rdba: 0x01800160 (6/352) TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x01800120.0486.02 SCN: 0x0000.0022c821 index state cflags wrap# uel SCN dba 0x05 9 0x00 0x0ad5 0x0006 0x0000.0022c829 0x01800120 0x06 9 0x00 0x0ad8 0xffff 0x0000.0022c832 0x01800121 buffer tsn: 6 rdba: 0x01800121 (6/289) UNDO BLK: xid: 0x0001.006.00000ad8 seq: 0x486 cnt: 0x1 irb: 0x1 icl: 0x0 flg: 0x0000 * Rec #0x1 slt: 0x06 objn: 70146(0x00011202) objd: 70146 tblspc: 5(0x00000005) 1 BH (0x673f4b40) file#: 6 rdba: 0x01800160 (6/352) class: 17 ba: 0x67328000 st: CR md: NULL tch: 1 buffer tsn: 6 rdba: 0x01800160 (6/352) … TRN CTL:: seq: 0x0486 chd: 0x0005 ctl: 0x0006 inc: 0x00000000 nfb: 0x0002 mgc: 0xb000 xts: 0x0068 flg: 0x0001 opt: 2147483646 (0x7ffffffe) uba: 0x0180011e.0485.02 SCN: 0x0000.0022c811 … index state cflags wrap# uel SCN dba ----------------------------------------------------------------------------------------- 0x05 9 0x00 0x0ad4 0x0006 0x0000.0022c818 0x0180011e 0x06 9 0x00 0x0ad7 0xffff 0x0000.0022c821 0x0180011f CR 블록 적용
  • 56. © Copyrights 2001~2016, EXEM CO.,LTD. All Rights Reserved. Oracle Deep Internal Blog Video E-mail NAVER http://cafe.naver.com/playexem ITPUB http://blog.itpub.net/31135309/ Wordpress https://playexem.wordpress.com/ Slideshare http://www.slideshare.net/playexem Youtube https://www.youtube.com/channel/UC5wKR_ -A0eL_Pn_EMzoauJg Tudou http://www.tudou.com/home/maxgauge/ 교육 문의 : 연구컨텐츠팀 김숙진 edu@ex-em.com