AWR and ASH Deep Dive

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AWR and Beyond Deep Dive, (Don’t Forget
EM12c!)
Oracle Confidential 2
Kellyn Pot’Vin-Gorman,
Consulting Member of Technical Team, Strategic Customer
Program
May, 2015

Safe Harbor Statement
The following is intended to outline our general product direction. It is intended for
information purposes only, and may not be incorporated into any contract. It is not a
commitment to deliver any material, code, or functionality, and should not be relied upon
in making purchasing decisions. The development, release, and timing of any features or
functionality described for Oracle’s products remains at the sole discretion of Oracle.

Stay on the Path…
• 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.

Brief History
• 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.

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

Automatic Workload Repository, (AWR) Reports
• 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;

Buffer writes one direction,
we read the other!

AWR Reports Are Best Used For..
• 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.

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.

SGA “Thrashing”

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.

RAC Cache Interconnect Stats

Transfer Rate Between RAC Nodes

ASH Reports
• 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.

Buffer writes one direction,
We read the other!

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

HTML Format ASH

Main ASH Info

Top SQL, Top Sessions

Top SQL Details

Top Parallel, Top DB Files

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:

“Interesting Part”

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

AWR and ASH from the CLI
All DBAs should know how to do this!

Running Reports, Command Line
$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.

AWR Info Report
• 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

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

SQL_ID Specific AWR Report

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

V$ACTIVE_SESSION_HISTORY
• 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.

Session Averages
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 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;

Results, Where to Focus?

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!

Wait Events Across Nodes

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

SQL_ID and CPU Usage

IO Waits by Object from ASH

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

Pivot the Wait Events

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
/

Results of Process History

Tyler Muth ASH Mining Query

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!

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

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

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

Full Detail of SQL Execution

View Report

SQL Monitor Report CLI
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;

Text Output of SQL Monitor

One of the Best & Least Used Features in EM
Search SQL
Problem Query

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

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

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

Snapshot Data

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

SQL Details

AWR Report or Run ADDM Report

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

AWR/ASH Links/Blogs
• 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/

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