DB2UDB_the_Basics Day2

 Tables
 Views
 Indexes
 Packages
 Procedures
 Triggers
 Pages
 Tablespaces
 Bufferpools
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 Tables are logical structure maintained by Database manager. In a table
each vertical block called as column (Tuple) and each horizontal block
called as row (Entity). The collection of data stored in the form of columns
and rows is known as a table. In tables, each column has different data
type.
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 System Catalog Tables
 User Tables
 Temporary Tables
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Each DB2 database has a set of tables called the system catalog tables.
DB2 creates these tables when a database is created.
• DB2 creates the system catalog base tables under the SYSIBM schema like
SYSIBM.SYSTABLES,SYSIBM.SYSVIEWS,SYSIBM.SYSPACKAGES.
• These tables are not erasable.
• DB2 optimizer uses these to track the changes happening to the db2
objects.
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All the tables created by DBAs will come under this category. All the tables
will be placed in usersapace1 table space by default
 db2 " create table customers (id integer primary key not null, name
varchar(50), age integer)”
 db2 " insert into customers values (11,‘abc',27)”
• db2 "select * from customers”
• db2 " select tabname, tabschema, tbspace from syscat.tables“
• db2 " select tabname, tabschema, tbspace from syscat.tables"| grep -i
customers
• db2 describe table customers
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Column name schema Data type name Length Scale Nulls
------------------------------- --------- ------------------- ---------- ----- ------
ID SYSIBM INTEGER 4 0 No
NAME SYSIBM VARCHAR 50 0 Yes
AGE SYSIBM INTEGER 4 0 Yes
db2 " alter table customers alter column ID set data type bigint"
------------------------------- --------- ------------------- ---------- ----- ------
ID SYSIBM BIGINT 8 0 No
NAME SYSIBM VARCHAR 50 0 Yes
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 db2 "alter table customers rename column NAME to NICKNAME”
------------------------------- --------- ------------------- ---------- ----- ------
ID SYSIBM BIGINT 8 0 No
NICKNAME SYSIBM VARCHAR 50 0 Yes
db2 "drop table customers“
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For temporary work of different database
operations, DB2 uses temporary tables. The
temporary tables do not appear in system catalog.
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View is an alternative way of representing the data stored in the tables. It is
not an actual table and it does not have any permanent storage. View
provides a way of looking at the data in one or more tables.
• db2 “create view view_sales1(id, itemname, qty, price) as select id,
itemname, qty, price from shopper.sales1”
• SYSIBM.SYSVIEWS ,SYSCAT.VIEWS
• db2 drop view <view_name>
• SYSCAT.TABLES, SYSCAT.VIEWS,SYSCAT.TABLESPACES are the
examples of view subjected to system catalog tables
SYSIBM.SYSTABLES,SYSIBM.SYSVIEWS and
SYSIBM.SYSTABLESPACES respectively.
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 Indexes are an ordered set of keys each pointing to a row in a table. They improve
application performance when looking for specific rows.
 Indexes are database objects that are built based on one or more columns of a table.
They are used for two main reasons:
 • To improve query performance. Indexes can be used to access the data faster
using direct access to rows based on the index key values.
 • To guarantee uniqueness when they are defined as unique indexes.
 SYSIBM.SYSINDEXES , SYSCAT.INDEXES
 db2 describe indexes for table customers show detail
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To create an index, use the CREATE INDEX statement. This statement requires at a
minimum:
• The name of the index
• The name of the associated table
• The columns that make up the index (also known as index keys)
In addition, you can specify the following:
• Whether the index is unique (enforce uniqueness for the key values) or non-
unique(allow duplicates)
• Which order DB2 should use to build and maintain the key values: ascending (ASC,
the default) or descending (DESC) order
• Whether to create INCLUDE columns that are not part of the index key but are
columns often retrieved by your queries
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 db2 “CREATE UNIQUE INDEX company_ix ON
company (company_ID ASC, name DESC)
INCLUDE (no_employees)”
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A package is a database object consisting of executable SQL, including the access
path the DB2 optimizer will take to perform the SQL operation.
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Procedures are programs whose executable binaries reside at the database server.
They serve as subroutines to calling applications, and they normally wrap multiple
SQL statements with flow logic. They are used to reduce the traffic so improving the
performance.
 Besides improving response time for applications running on a different server than
the database server, stored procedures also provide a central location to store
database application logic. This allows for a single place to maintain your code.
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There are 2 types of procedures in DB2 .
1. Fenced Procedure
2. Unfenced Procedure
A fenced stored procedure runs in a different address space than the DB2
engine. This guarantees that a failure from the procedure will not corrupt the
DB2 engine itself. In Linux and UNIX, a fenced user needs to be created to
work with fenced stored procedures.
 In terms of performance, unfenced stored procedures run faster than fenced
ones; however, there is a risk that unfenced procedures may corrupt DB2
information,
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A trigger is a database object associated to a table or a view that contains some
application logic, which is executed automatically upon an INSERT, UPDATE, or
DELETE operation on the table or view.
Triggers can be classified as BEFORE, AFTER, or INSTEAD OF triggers.
Example of Before Trigger
 CREATE TRIGGER default_time NO CASCADE BEFORE INSERT ON schedule
REFERENCING NEW AS n FOR EACH ROW MODE DB2SQL
WHEN (n.start_time IS NULL) SET n.start_time = '12:00'
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 CREATE TRIGGER audit_qty
 AFTER UPDATE OF quantity ON inventory
 REFERENCING OLD AS o NEW AS n
 FOR EACH ROW
 MODE DB2SQL
 INSERT INTO sold
 VALUES (n.product_ID, n.daysold, o.quantity - n.quantity)
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 This example demonstrates how a read-only view can still be updated by
using INSTEAD OF triggers. In the example, the trigger updates the region
column of table table2 when the view view2 (a read-only view) is updated.
 CREATE TRIGGER update_view2 INSTEAD OF UPDATE
 ON view2 REFERENCING OLD AS o NEW AS n
 FOR EACH ROW MODE DB2SQL
 BEGIN ATOMIC UPDATE table2
 SET region = n.region
 WHERE region = o.region;
 END
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DB2 stores table and index data on a page, which is the smallest unit of storage in a DB2
database.
 DB2 creates and manages the pages in the table space automatically, but you can control
the page size for your table spaces. If you do not explicitly specify the page size when you
create
 the table space, DB2 will use the default size of 4K. DB2 supports four different page sizes:
4K,8K, 16K, and 32K.
 The maximum number of rows on a page is 255 rows. This is significant, if you have small
row sizes.
 A table space may contain up to 64 GB of data, if the page size is 4K.
 Chunk of pages are called as Extent
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A table space is a storage structure, it contains tables, indexes, large
objects, and long data. It can be used to organize data in a database into
logical storage group which is related with where data stored on a system.
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 The table spaces are beneficial in database in various ways given as
follows:
 Recoverability: Tablespaces make backup and restore operations more
convenient. Using a single command, you can make backup or restore all
the database objects in tablespaces.
 Automatic storage Management: Database manager creates and extends
containers depending on the needs.
 Memory utilization: A single bufferpool can manage multiple tablespaces.
You can assign temporary tablespaces to their own bufferpool to increase
the performance of activities such as sorts or joins.
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When you create a new database, the database
manager creates some default tablespaces for
database. These tablespace is used as a storage
for user and temporary data. Each database must
contain at least three tablespaces as given here:
 Catalog tablespace
 User tablespace
 Temporary tablespace
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Logical layer between Hardware and Database
Comprised of one or more containers
A container is a file or a directory
REGULAR
CREATE TABLESPACE name
LARGE
SYSTEM
TEMPORARY
USER
MANAGED BY SYSTEM system-containers
DATABASE database-containers

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SMS Containers
USING (‘container string’)
DMS Containers
USING (FILE ‘container string’ number of pages)
(DEVICE ‘container string’ number of pages)

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CREATE TABLESPACE TS1 MANAGED BY SYSTEM
USING (‘/home/inst01/database/ts1’)
CREATE TABLESPACE DMS01D MANAGED BY DATABASE
USING (FILE ‘C:DMSDATABASEDMS01D’ 1000)

The database buffer pool area is a piece of real memory that is used by DB2
to temporarily store (cache) the regular data and index pages when they are
read from disk to be scanned or modified.
 The buffer pool area improves the performance of the database, since the
pages can be accessed
 much more quickly from memory than from disk.
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 When you create a database, DB2 creates a default buffer pool named
IBMDEFAULTBP.
 CREATE BUFFERPOOL tempbp SIZE 10000
 ALTER TABLESPACE tempspace1 BUFFERPOOL tempbp
 CREATE BUFFERPOOL bp16k SIZE 100000 PAGESIZE 16K
 ALTER BUFFERPOOL bp16k SIZE 200000
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You will not be able to drop any buffer pools that are
associated with a table space. Before you can drop the
buffer pool you will need to associate the table space
with a different buffer pool using the ALTER
TABLESPACE statement.
DROP BUFFERPOOL bp16k
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 db2 get snapshot for bufferpools on database-name
Bufferpool name = IBMDEFAULTBP
Database name = MUSICKEG
Database path = C:DB2NODE0000SQL00002
Input database alias = MUSICKEG
Snapshot timestamp = 05/04/2005 13:11:37.329018
Buffer pool data logical reads = 336
Buffer pool data physical reads = 129
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 IMPORT
 EXPORT
 LOAD
 db2move
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IMPORT FROM filename OF IXF
DEL
ASC
LOBS FROM lob-path MODIFIED BY options
MESSAGES
INSERT INTO table-name
INSERT_UPDATE
REPLACE
REPLACE_CREATE

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EXPORT TO file OF IXF MESSAGES message-file
DEL
WSF
select statement

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1) Load Loads data, collects index keys
2) Build creates the indexes
3) Delete Delete unique key violations place into
exception tables.
4) Index Copy – copy indexes from temp table space

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LOAD FROM filename OF IXF
ASC
DEL
LOBS FROM lob-path MODIFIED BY options
MESSAGES message-file
INSERT INTO table-name
REPLACE
RESTART
TERMINATE

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Create nickname sales for
another database SAMPLE table SALES
Create nickname employee for
another database SAMPLE table EMPLOYEE
DECLARE C1 CURSOR FOR SELECT SALES.SALES_PERSON,
LASTNAME, FIRSTNME FROM SALES, EMPLOYEE
WHERE SALES_PERSON = EMPLOYEE.LASTNAME
LOAD FROM C1 OF CURSOR INSERT INTO LOCAL_SALES

db2move
Database
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db2move.lst
table.ixf
DB2MOVE

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db2move database-name import
export
load
tc table-creators
tn table-name
sn schema-names
ts table space-names

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CREATE TABLESPACE TS1 MANAGED BY SYSTEM
USING (‘C:SMSMUSICKEGTS1’)
CREATE TABLESPACE DMS01D MANAGED BY DATABASE
USING (FILE ‘C:DMSMUSICKEGDMS01D’ 161)
EXTENTSIZE 8 PREFETECHSIZE 8
CREATE TABLESPACE DMS01I MANAGED BY DATABASE
USING (FILE ‘C:DMSMUSICKEGDMS01I’ 48)
EXTENTSIZE 4 PREFETCHSIZE 4

Defining logs
Recovery of database
Recovery of a table space
Offline versus Online
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Database
S0000000.log
S0000001.log
S00000002.log
S0000003.log(SecondaryLog)
S0000004.log(SecondaryLog)
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Database
S0000000.log
S0000001.log
S00000002.log
S0000003.log
S0000004.log
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 If LOGRETAIN = Recovery you may backup table space
or database
 If LOGRETAIN = NO you may only backup database
BACKUP DB database-name ONLINE to C:backup
INCLUDE LOGS
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 If LOGRETAIN = NO, you may only recover the
database
 If LOGRETAIN = RECOVERY, you may recover a table
space or a database from a full database backup
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 Offline
 Online
RESTORE DB database-name FROM file TAKEN AT
time
ROLLFORWARD DATABASE database-name
TO isotime AND STOP
END OF LOGS
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Database_standby
Database1
Laptopcomputer
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 Database Configuration parameters
 Database Structure
 SQL Statements
55

Database
BufferPool
Select*fromStaff
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 Sorts are done in sortheap
 If no space for sort data is moved to TEMPSPACEn
 GET SNAPSHOT FOR ALL ON database
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 Dynamic SQL statements
PackageCache
Select*fromStaffwhereID=10
Select*fromStaffwhereID=10
UpdateStaffSetSalary=Salary+100whereID=10
Select*fromEMPLOYEE
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 Locks are held to prevent loss of data
 Lock Row / Table / Table Space
 LOCKLIST
 MAXLOCKS
 ALTER TABLE table-name LOCKSIZE TABLE
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 Determine which statement is causing the majority of
problems
 Determine what might be causing the problem
 Testing the solution
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 Buffer pools
 Numerous Database Configuration parameters
 SQL Statement Tuning
67

 Security is used at the operating system level
 Table access is through the database
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 SYSADM_GROUP
 SYSCTRL_GROUP
 SYSMAINT_GROUP
 SYSMON_GROUP
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 GRANT access to an object/program
 REVOKE access to an object/program
 GRANT SELECT ON TABLE ARTISTS TO
USER1
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 The Relational Database can be simple or complex
 The database structure is simple, Table spaces, Tables,
etc.
 Recovery is straight forward
 Database maintenance can be automated
 Tuning the database is a life long endeavor
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 July 12, 13 DB2 UDB Administration Proof of
Technology
 IBM – McClean Tec
 8401 Greensboro Drive
 McClean, VA 22102
 Suite 120 First Floor
 WebSphere Information Integrator July 14, 2005
 Contact: Keith E. Gardenhire
 keithgar@us.ibm.com
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DB2UDB_the_Basics Day2

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