ASH and AWR on DB12c

© 2015 Delphix. All Rights Reserved. Private & Confidential.
Performance Data in Database 12c
Knowledge is Power
AWR and ASH with EM13c
Kellyn Pot’Vin-Gorman, Technical Intelligence Manager
October 2016

• Optimization- Tune for Time or You’re Wasting Time.
• Know your goal(s)
• Set a stopping point, avoid OTD, (Obsessive Tuning Disorder)
• Do NOT assume. Always do the research and have data behind findings.
Stay on the Path…

• ASH= Active Session History
• AWR= Automatic Workload Repository
• Introduced in Oracle 10g
• Evolution to statspack, requests for performance reporting improvements.
• “Always on” approach to performance metrics with requirement of non-
locking collection process.
• Requires Management Diagnostic Pack License from Oracle.
Brief History

The Location in EM12c For Some of Today’s Presentation…

 Always on with default intervals of 1hr snapshots and 8 days retention.
 Should have at least 60 days of retained data.
 Desire more? Have an AWR Warehouse.
 Interval increase? Use this during workload testing, otherwise, take a manual
snapshot:
EXEC DBMS_WORKLOAD_REPOSITORY.create_snapshot;
Automatic Workload Repository, (AWR) Reports

Buffer writes one direction,
we read the other!

• To inspect a database level issues, for both a small window of time to extended
window.
• Extensive information in report, knowing HOW to parse through the report to achieve
goal is important.
• Via EM12c, the report is offered in HTML format and will be environment aware,
(single instance, RAC, Exadata.)
• Different reports available from the command line when running from the
$ORACLE_HOME/rdbms/admin directory and can be generated in HTML or TXT
format.
AWR Reports Are Best Used For..

Wasting Time…. 
Rarely is there value in this section.
As long is everything contains high percentages, move on.

AWR- Top 10 Foreground
•CPU is expected and should be the majority of time.
•CPU processing can be extensive though, (still needs to
be investigated)
•Anything under 10% commonly is disregarded.
•Understand what each wait event definition is

Top SQL
Focus on Elapsed Time, but…
Displays Top SQL by:
CPU
IO
Gets
Reads, etc…

Full SQL Statements
Linked from Top SQL Lists in HTML report via SQL_ID links.
Quick reference when needed.

Why PGA is Important
What is an optimal vs. 1 or (M)ulti-pass executions?

Why Can’t I Achieve 100%??
You shall not pass! (optimal, so 90%, that is… )

Percentages and Amounts of Reads are Important
Top two objects correspond to SQL statements in the top IO
and most likely top SQL by elapsed time.

What is a Direct Physical Read?
•Inefficient SQL and objects that have high quantity of row changes involved.
•Adds significant pressure in RAC environment, too!

Un-optimized vs. Optimized?
Percentages are low per object, (under 10%, which is a good sign for any database!)
This is an exadata, so it means they are either not in the buffer cache or the smart flash
cache, which means un-optimized”.
This is “somewhat” expected and don’t panic unless you see high percentages.

Initial Transaction Locks
10% rule applies here, too!
ALTER TABLE <name> initrans <xx>;

RAC Interconnect Exchange
•Data from V$SYSMETRIC_HISTORY
•High Exchange rate can signal and issue.

Transfer Rate Between RAC Nodes

• Excellent for identifying specific issues in database.
• Identifies not just the top SQL, but code.
• Shows top wait events by sample time.
• Don’t confuse samples with AWR snapshots.
• Should not be used to track # of executions.
ASH Reports

Buffer writes one direction,
We read the other!

Running ASH Report from Cloud Control
• ASH is by time, not snapshot.
• Set start date and time.
• End date and time
• Generate report

ASH Report- Use Case
@$ORACLE_HOME/rdbms/admin/ashrpt.sql;
 Report Format: Text
 Performance Issue during day, need to know what’s going on!
 Run ASH Report from the command line with SQL*Plus:

Finally!
Select * from table(dbms_xplan.display_awr(‘43mp3mjufgnkg’));

AWR and ASH from the Command Line Interface
All DBAs should know how to do this!

$ORACLE_HOME/rdbms/admin/awrrpt.sql;
$ORACLE_HOME/rdbms/admin/ashrpt.sql;
$ORACLE_HOME/rdbms/admin/awrsqrpt.sql;
Less Known AWR Reports:
awrinfo.sql General AWR Info
awrddrpt.sql Comparison report between snapshots
awrblmig.sql Migrates pre-11g baseline data into 11g Baseline tables.
awrgrpt.sql RAC Aware AWR Report.
Running Reports, Command Line

 Snapshot Interval Information
 Basic Info on Instances and Nodes
 No User or Application Schema info.
 Space Usage by SYSAUX
 WRH$ and Non- AWR Objects, ordered by size
 Snapshot info and if any errors.
 Advisor Tasks
AWR Info Report

AWR General Information Report

ASH Info Report
@$ORACLE_HOME/rdbms/admin/ashrpt.sql;
 Report Format: Text or HTML

• More defined reporting
• No need to pull full report
• Detail on waits that are of interest
• Join to non-AWR objects
• Examples and Ideas…
Querying ASH Data Directly

• SAMPLE_ID- This is a unique identifier within an ASH sample.
• SAMPLE_TIME- A unit of time used by Active Session History, (not to be confused with
DB_TIME)
• USER_ID- Identifier for a user that’s executing the session.
• SESSION_ID- Same as the SID or Session ID and can be used to join to SID in other
views/tables.
• SESSION_STATE- What was the state of the session when ASH recorded the sample.
• ON CPU/WAITING- The two session states in Active Session History. ON CPU is active,
vs. Waiting, which is self-explanatory.
• EVENT- Type of event that the session is currently active or waiting on.
• TIME_WAITED- How long the session has been waiting if waiting.
• WAIT_TIME- Confusing- but this is populated by any wait time if the session is currently
active and for the previous waits.
• SQL_ID- The unique identifier for the SQL statement being executed.
• SQL_CHILD_NUMBER-The cursor child number.
V$ACTIVE_SESSION_HISTORY

Select ROUND(RATIO_TO_REPORT(SUM(1)) OVER () * 100 ,2)
PERCENTAGE,ash.session_type SESS_TYPE,
session_state STATUS, decode(nvl(sql_id,'-1'),'-1','nonsql','sql')
SQL_TYPE,
count(distinct to_char(session_id)|| to_char(session_serial#))
SESS_CNT
from v$active_session_history ash
where
sample_time > sysdate - 30/(24*60) and (
( ash.session_state = 'ON CPU’ ) or
( ash.session_type != 'BACKGROUND' ))
group by ash.session_type,
ash.session_state, decode(nvl(sql_id,'-1'),'-1','nonsql','sql')
order by count(*)
/
Session Averages

Session Avg. Output
• Note the % of Background processes

Inspecting What
select * from (select ash.SQL_ID , ash.SQL_PLAN_HASH_VALUE Plan_hash, aud.name
type,
sum(decode(ash.session_state,'ON CPU',1,0)) "CPU",
sum(decode(ash.session_state,'WAITING',1,0)) "WAITING",
sum(decode(ash.session_state,'WAITING', decode(wait_class, 'User
I/O',1,0),0)) "IO WAIT" ,
sum(decode(ash.session_state,'WAITING', decode(wait_class, 'User
I/O',1,0),0)) "IO" ,
sum(decode(ash.session_state,'WAITING', decode(wait_class,
'Concurrency',1,0))) "CONCURRENCY" ,
sum(decode(ash.session_state,'WAITING', decode(wait_class,
'Application',1,0))) "Application" ,
sum(decode(ash.session_state,'ON CPU',1,1)) "TOTAL"
from v$active_session_history ash, audit_actions aud where SQL_ID is not NULL
and ash.sql_opcode=aud.action and ash.sample_time > sysdate - &minutes /(
60*24)
group by sql_id, SQL_PLAN_HASH_VALUE , aud.name
order by sum(decode(session_state,'ON CPU',1,1)) desc
) where rownum < 5;

10 Min. View of Waits by SQL_ID
• Choose Time in Minutes To Review, (10 in our
example)
• SQL_ID and Plan Hash Value Shown
• Waits for CPU, Wait, IO Wait and others.

Quantity of Events Occurred Over
Small Amounts of Time
Col event for a50
select event, count(1)
from v$active_session_history
where sample_time between
to_date('21-FEB-14 01.43.00 PM','dd-MON-yy hh:mi:ss
PM')
and
to_date('21-FEB-15 01.53.00 PM','dd-MON-yy hh:mi:ss
PM')
group by event
order by event;

Transaction Wait Detail
select to_char(sample_time,'HH:MI') st,
substr(event,0,20) event,
ash.session_id sid, mod(ash.p1,16) lm, ash.p2,
ash.p3, nvl(o.object_name,ash.current_obj#) objn,
substr(o.object_type,0,10) otype, CURRENT_FILE# fn,
CURRENT_BLOCK# blockn, ash.SQL_ID, BLOCKING_SESSION
bsid
from v$active_session_history ash, all_objects o
where event like 'enq: TX%'
and o.object_id (+)= ash.CURRENT_OBJ#
and sample_time > sysdate - 10/(60*24)
order by sample_time;

Transaction Lock Output
 What TX row locks are occurring!

Knowing What’s in the ASH Buffer
Deters from making assumptions on what data is being
queried.
Know your samples!

Query top
10 SQL_ID’s
in the last
10 minutes?

SQL Text with ASH
SQL for most recent five minutes of sample data from ASH

SQL Results
SQL_ID, SQL Text, Sample Time that Process was captured
in.

Graphing From the CLI, via Kyle Hailey-

Formatting and Setup
accept hours prompt "hours (default 12) : " default 12
select &hours f_hours from dual;
select 3600 f_secs from dual;
select &v_secs f_samples from dual;
select 30 f_graph from dual;
select to_char(to_date(tday||' '||tmod*&v_secs,'YYMMDD SSSSS'),'DD-MON
HH24:MI:SS') tm,
samples npts,total/&samples aas,
substr(substr(substr(rpad('+',round((cpu*&v_bars)/&samples),'+') ||
rpad('-',round((waits*&v_bars)/&samples),'-') ||
rpad(' ',p.value * &v_bars,' '),0,(p.value * &v_bars)) ||
p.value || substr(rpad('+',round((cpu*&v_bars)/&samples),'+') ||
rpad('-',round((waits*&v_bars)/&samples),'-') ||
rpad(' ',p.value * &v_bars,' '),(p.value * &v_bars),10) ,0,30)
,0,&v_graph)graph,total,cpu, waits from (
URL to Kyle Hailey’s Original, Fully Formatted Query

select to_char(sample_time,'YYMMDD')tday
, trunc(to_char(sample_time,'SSSSS')/&v_secs) tmod ,
sum(decode(session_state,'ON CPU',1,decode(session_type,'BACKGROUND',0,1))) total
, (max(sample_id) - min(sample_id) + 1 ) samples ,
sum(decode(session_state,'ON CPU' ,1,0)) cpu
, sum(decode(session_type,'BACKGROUND',0,decode(session_state,'WAITING',1,0)))
waits
from v$active_session_history where sample_time > sysdate - &v_hours/24
group by trunc(to_char(sample_time,'SSSSS')/&v_secs),
to_char(sample_time,'YYMMDD')
union all
select to_char(sample_time,'YYMMDD')tday,
trunc(to_char(sample_time,'SSSSS')/&v_secs) tmod
, sum(decode(session_state,'ON CPU',10,decode(session_type,'BACKGROUND',0,10)))
total
, (max(sample_id) - min(sample_id) + 1 ) samples, sum(decode(session_state,'ON
CPU' ,10,0)) cpu
, sum(decode(session_type,'BACKGROUND',0,decode(session_state,'WAITING',10,0)))
waits
from dba_hist_active_sess_history where sample_time > sysdate - &v_hours/24 and
sample_time < (select min(sample_time) from v$active_session_history)
group by trunc(to_char(sample_time,'SSSSS')/&v_secs),
to_char(sample_time,'YYMMDD')) ash, v$parameter p
where p.name='cpu_count'
order by to_date(tday||' '||tmod*&v_secs,'YYMMDD SSSSS'); **Thanks to Kyle Hailey for this great graph via the CLI

Digging into History
• DBA_HIST_ACTIVE_SESS_HISTORY
 SNAP_ID
 SAMPLE_ID
 SAMPLE_TIME
 SESSION_ID
 USER_ID
 SQL_ID
 WAIT_CLASS
 SESSION_STATE
 PGA_ALLOCATED

Process Information
SELECT * FROM (
SELECT /*+ PARALLEL */
count(*) AS count,
user_id, program, module, sql_id
FROM SYS.DBA_HIST_ACTIVE_SESS_HISTORY
WHERE sample_time > TO_DATE('19-FEB-2014 03.00.00 PM','dd-MON-yy
hh:mi:ss PM')
AND sample_time < TO_DATE('19-FEB-2014 08.00.00 PM','dd-MON-yy
hh:mi:ss PM')
AND program LIKE 'oracle@%'
GROUP BY user_id, program, module, machine, sql_id
ORDER BY count(*) desc
)
WHERE rownum <= 20
/

ASH Mining Output
Additional Options:
• Physical Read Averages
• Physical Writes, (Max/Averages)
• Redo Info
• Login Info
• Hard Parsing, etc.

Best Practice When Querying ASH Data
 Keep it Simple and don’t reinvent the wheel.
 Again- samples are an alias for time, not for counts.
 Understand what is valuable and compare to packaged
reports.
 Be aware on RAC of node specific data.
 Take care when querying Obj#, File# and Block#, (still issues
in different versions…)
 Check the time that is available in buffer, don’t assume!

• One More way to identify performance issues.
• Monitoring view ease for those less familiar with database performance.
SQL Monitor, EM12c Style

SQL Monitor Dashboard
Status of Statement
Wait Events
Degree of
Parallelism
SQL_ID
SQL Text

• Drill down to specific statement within SQL Monitor will display offload efficiency per
statement.
Exadata and Offloading

SET LONG 1000000
SET LONGCHUNKSIZE 1000000
SET LINESIZE 1000
SET PAGESIZE 0
SET TRIM ON
SET TRIMSPOOL ON
SET ECHO OFF
SET FEEDBACK OFF
SELECT DBMS_SQLTUNE.report_sql_monitor(
sql_id => '5vh6y3b7tnv8r',
type => 'TEXT',
report_level => 'ALL') AS report
FROM dual;
SQL Monitor Report via the Command Line Interface

One of the Best & Least Used Features in Enterprise
Manager: Search SQL
Problem Query

4v2tsp8dz0nhn is our SQL_ID
Go to the EM Console, (Example is EM12c)
We Have the SQL_ID, What Next?

 Choose AWR Snapshots, (change Time Period), AWR Baselines and put SQL_ID
Search SQL Interface

 SQL_ID link for SQL Details
 Split up by tabs for Cursor, AWR, Baselines and SQL Tuning Sets
 Plan Hash Value
 Elapsed Time
Click on Search

 Using the information provided by Search SQL, locate the correct plan hash value to
create a profile from.
Identify

Baseline Impact?
Third Tab contains Baseline Information and links to verify if implemented.

• Tyler Muth: http://tylermuth.wordpress.com/
• Kyle Hailey, John Beresniewicz, Graham Wood: http://ashmasters.com/
• Mine- “For the Love of ASH and AWR” http://dbakevlar.com/2011/02/for-the-love-of-
awr-and-ash/
• Using AWR Reports: http://dbakevlar.com/2015/01/working-with-awr-reports-from-
em12c/
• How to Use an ASH Report: http://dbakevlar.com/2015/02/how-to-use-an-ash-report-
and-why/
• SQL ID Specific Performance Information: http://dbakevlar.com/2015/05/sql-id-
specific-performance-information/
AWR/ASH Links/Blogs

@DBAKevlar
https://dbakevlar.com http://delphix.com
kellyn@delphix.com
https://linkedin.com/in/kellynpotvin
Connect With Me

ASH and AWR on DB12c

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ASH and AWR on DB12c