AWR and ASH Advanced Usage with DB12c

Performance Data in Database 12c
AWR and ASH with EM13c
Kellyn Pot’Vin-Gorman, Technical Intelligence Manager for the Office of CTO
October 2016

2© 2016 Delphix Corporation
Who am I?

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.

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

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

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”

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

SQL_ID Specific AWR Report

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

Note the % of Background processes
Session Avg. Output

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;
Inspecting What

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.
10 Min. View of Waits by SQL_ID

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;
Quantity of Events Occurred Over Small Amounts of Time

Results, Where to Focus?

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 Wait Detail

What TX row locks are occurring!
Transaction Lock Output

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-

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 (
Formatting and Setup
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

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

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
/
Process Information

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.

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!
Best Practice When Querying ASH Data

It ran fine last week, now it doesn’t!
ETL loads have changed, but no one has released any new code!
The DBA says there hasn’t been any parameter changes to this database, but
I’m sure there have been.
Compare ADDM Resolution
How Often Are We Asked, “What Changed?”

Uses Two AWR snapshots
Creates Report that-
- Compares SQL that is common and different.
- SGA changes
- IO/CPU bound issues
- Parameter Changes
What is Compare ADDM?

Report Includes Following:
- Clear Demonstration of impact of change.
- Recommendations to address issue.
- Identifies causes behind change, (with limitations.)
- Lists Regressed SQL, too!
- Tip: If Installing to database for first time, (simple installation, nothing to
concern about, just pkg to fulfill views) you must have preferred
credentials SET of install will fail!
What is in an ADDM Compare?

Choose focus period
Choose to compare to an Offset, Baseline or Custom
Executing a Report from EM12c

Familiar interface with visual wait event comparisons.
Average # of sessions during each period are displayed.
2-3PM, 12th Vs. 13th

High level data, highlight for analysis and recommendations.
Detail Report

Any performance degradation is noted with the down arrow icon:
Regression SQL

High Level data
Click on “Show Hot Object Breakdown” to see more detail.
Top Segments Causing IO Waits

Comparisons of Memory, CPU, IO and Interconnect.
Memory Is there Virtual paging?
 Memory Base Period
 Memory Comparison Period
Resource Comparisons

Is something OTHER than Oracle the cause?
Dashboard Provided for CPU, Memory, IO and Interconnect

IO Bound Dashboard
 Base vs. comparison period
 Temp reads/writes specified
 Single block read latency

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

SQL Monitor Dashboard

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

Full Detail of SQL Execution

View Report

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

Text Output of SQL Monitor

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

Snapshot Data

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

SQL Details

AWR Report or Run ADDM Report

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

Q&A
Thank you!

AWR and ASH Advanced Usage with DB12c

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