10 steps to analyze awr report in oracle

7/26/2019 10 Steps to Analyze AWR Report in Oracle

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As you have Generated AWR Report in

Oracle, Next task is to Analyze AWR

Report in Oracle. By Reading AWR

Report you can easily solve issues like

Slow database, high wait events, Slow

query and many more. Though It's a

lengthy report but Analyzing or

Reading relevant part of AWR Report

can help to troubleshoot issues in easy

and fast manner.

AWR stands forAutomatically

workload repository, Though there

could be many types of database

performance issues, but when whole

database is slow, then there are two

possibilities.

1. Issue with Database Machine. OS Watcher is the best tool to start.

2. If Database performance issue, Then AWR Report is the place to look

at.

In case if a particular query is not performing well, i would suggest to look at execution plan of the

query, stats of underlying table etc. In this case AWR won't help much.

Recommendations before getting an AWR Report.

1. CollectMultiple AWR Reports:It's always good to have two AWR Reports, one forgood time (when database was performing well), second when performance is poor. This way

Remote DBA can easily compare good and bad report to find out the culprit.

2. Stick to Particular Time: "Database is performing slow" will not help anymore to resolveperformace issues. We have to have a specific time like Database was slow yesterday at 1 Pm and

continue till 4Pm. Here, DBA will get a report for these three hours.

3. Split Large AWR Report into Smaller Reports:Instead of having one report forlong time like one report for 4hrs. it's is better to have four reports each for one hour. This will help

to isolate the problem.

In case of RAC env. generate one report for each instance. Once, you have generated AWR report.

Now, it's time of analyze the report. Since, AWR report is a huge report and area to look into AWR

is also depends on problem to problem. Here, I am list most common area for a DBA to look into

which will give a clear picture of the issue.

Steps to Analyze AWR Report

1. Database Details:

After getting an AWR Report This is first and Top part of the report. In this part cross check for

databaseand instanceand and database versionwith the Database having performance

issue.This report also show RAC=YESif it's an RAC database.

2. Host Configuration:

This will give you name, platform CUP, socketand RAM etc. Important thing to notice is number

of cores into the system. In this example there are 12 CUP's inCores.

3. Snap Shot Detail:

This are the detail about snap shot taken,Snap start timeandend time. Difference between them

is as "Elapsed". Here is a new term "DB Time"

DB Time= session time spent in database.

DB Time= CPU Time + Non IDLE wait time.

You can find, DB time is very large as comparedto Elapse time, which is not a concern. Check if

you have taken a report for the time having performance problem. If yes fine, other wise take a

report for performance problem time.

Next is CacheSizes, which is just detail about SGA components.

4. Load Profile:

Here are few important stats for a DBA to look into. Fist is "DB CPU(s)" per second. Before that

let's understand how DB CUP's work. Suppose you have 12 cores into the system. So, per wall

clock second you have 12 seconds to work on CPU.

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let's understand how DB CUP's work. Suppose you have 12 cores into the system. So, per wall

clock second you have 12 seconds to work on CPU.

So, if "DB CPU(s)" per second in this report > coresin (Host Configuration (#2)).

means env is CPU bound and either need more CPU's or need to further check is this happening

all the time or just for a fraction of time. As per my experience there are very few cases, when

system is CPU bound.

In this case, machine has 12 cores and DB CPU(s) per second is 6.8. So, this is not a CPU

bound case.

Next stat to look at are Parsesand Hard parses. If the ratio of hard parse to parse is high, this

means Database is performing more hard parse. So, needs to look at parameters likecursor_sharing and application level forbindvariables etc.

5. Instance Efficiency Percentages:

In these statistics, you have to look at "% Non-Parse CPU". If this value is near 100% means most

of the CPU resources are used into operations other than parsing, which is good for database

health.

6. Top 5 Timed Foreground Events:

This is another most important stats to consider while looking at AWR Report for any database

performance related issue. This has a list of top 5 foreground wait events.

Here, first of all check forwait classif wait class is User I/O , System I/O, Others etc this could be

fine but if wait class has value "Concurrency" then there could be some serious problem. Next to

look at is Time (s)which show how many times DB was waiting in this class and then AvgWait

(ms). IfTime(s)are high but Avg Wait (ms)is low then you can ignore this. If both are high or Avg

Wait (ms)is high then this has to further investigate.

In the above screen shot, most of the resource are taken by DB CPU = 64% DB time. Taking

resource by DB CUP is a normal situation.

Let's take an example, In which event is "log file switch (checkpointincomplete) " which has high

waits, huge Time (s)and large valuesin Avg Wait (ms)and wait classis configuration. So, here

you have to investigate and resolve log file switch (checkpoint incomplete).

Host CPU, Instance CPU and Memory Statist ics are self explanatory. Next is RAC Statistics, I did

not find any issue in these stats most of the time.

7. Time Model Statistics:

This is a detailed explanations of system resource consumptions. Stats are order by Time (s) and

% of DB Time.


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Labels: Performance Tuning

A noticeable result Sum of all % of DB time is > 100%. why is this ?

Because this is cumulative time i.e. In this case SQL execute elapsed time is taking 89% of DB

time, which includes it sub parts like parse time elapsed, hard parse elapsed time etc. So, if you

find Hard parse time elapsed is taking more %. So investigate further so on and so forth.

DBA has to look for stat which is taking abnormal % of DB time.

8. Operating System Statistics - Detail:

This is the information related to OS, what is the load status on System shown here.

This report shows, system is 62 and 70% idle at time of report taken, So, there is no resource

crunch at system level. But if, you found very high busy, user or sys % and indeed this will led to

low idle %. Investigate what is causing this. OS Watcher is the toolwhich can help in this direction.

Next, very crucial part of AWR report for a DBA is SQL Statistics. Which has all sql query details

executed during report time interval.

We will explore few of them, To understand, how to analyzed these reports. Let's start with

9. SQL Ordered by Elapsed Time:

As explained by name itself, this lists SQL queries ordered byElapsed timeinto reported time

interval.

In this report, look for query has low executions and highElapsed time per Exec (s)and this

query could be a candidatefor troubleshooting or optimizations. In above report, you can see first

query has maximum Elapsed time but no execution. So you have to investigate this.

In Important point, if executions is 0, it doesn't means query is not executing, this might be the case

when query was still executing and you took AWR report. That's why query completion was not

covered in Report.

10. SQL Ordered by CUP Time:

In this report, SQL queries are listed on the basis of CPU taken by the query i.e. queries causinghigh load on the system. The top few queries could be the candidate query for optimization.

From above

stat, look for queries using highest CPU Times, If a query showsexecutions0, this doesn't means

query is not executing. It might be same case as in SQL queries ordered by Elapsed time. The

query is still executing and you have taken the snapshot.

However, There are so many other stats in AWR Report which a DBA needs to consider, I have

listed only ten of them but these are the most commonlyused stats for any performance related

information.

Please share you view about this article, Does it helps you to understand, How to analyze AWR

Report.

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Labels: Performance Tuning

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45 comments:

Anonymous July 2, 2013 at 10:35 AM

Nice article, me also working in oracle side as a TechArch.

Keep n touch

Thanks

Vijay

Bangalore

[email protected]

Reply

umesh sharma July 2, 2013 at 9:29 PM

Vijay, Thanks for your comments.

Amit Pal December 30, 2013 at 2:28 AM

there are 10 stats discussed and all are very clear to me now..hope u will show some

other stats as well..thanks a lot.

Regards

Amit Pal

Anonymous June 8, 2015 at 1:15 AM

Hi Umesh,

Keep up the good work !!!

Tx

Anonymous August 20, 2015 at 6:29 AM

Hi,

It was really a nice starts for performance tuning. Please share some more explanation

on the same to dig more to AWR Report.

Rishiraj Chockraborty September 2, 2013 at 11:37 PM

Very Good article....thanks for sharing this....

Reply

umesh sharma September 4, 2013 at 7:33 AM

Thanks for your complement.

Unknown September 12, 2013 at 3:42 AM

Very nice article.....thanks for sharing...also share some books & tips which have detail information

and analysis of AWR,ASH & ADDM Report.

Thanks & Regards

Vaibhav Jain

Jr. Oracle [email protected]

Reply

umesh sharma September 12, 2013 at 4:30 AM

Vaibhav, Thanks for your appreciation.

Reply

feroz shaik October 28, 2013 at 7:56 AM

great doc!! Really appreciate it.

Reply

feroz shaik October 28, 2013 at 7:57 AM

Great Doc!! Really appreciate it. Many Thanks.

Reply

umesh sharma October 28, 2013 at 9:23 AM

Thanks Feroz

Padma December 3, 2013 at 3:29 AM

Thanks for Sharing the document, i ts good analysis of AWR Report.


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Thanks for Sharing the document, i ts good analysis of AWR Report.

Thanks & Regards,

Padma

Jr. Oracle DBA

[email protected]

Reply


Thanks for Document its good analysis for AWR report :)

Reply

umesh sharma December 4, 2013 at 1:08 AM

Thanks friends.

Reply

naru lc December 10, 2013 at 2:04 AM

Nice explanation.. Thank you..

Reply

naru lc December 10, 2013 at 2:06 AM

Nice explanation.. Thanks a lot.

May I also request you to post similar blog to analyze DB when it is under peak load using ASH?

Thanks in advance..

Reply

umesh sharma December 10, 2013 at 2:09 AM

Thanks friend.

Anonymous January 3, 2014 at 3:59 AM

Really this article helped me alot.Thanks Umesh

Reply

umesh sharma January 3, 2014 at 4:07 AM

Thanks friend.

Sharv Gupta January 17, 2014 at 11:20 PM

Thanks a lot Umesh for this useful article.

Reply

umesh sharma January 19, 2014 at 8:58 AM

Thanks dear.

Gaurav Sharma February 19, 2014 at 10:17 AM

It is very informative .

Thanks

Reply

Gaurav Sharma February 19, 2014 at 10:19 AM

It's a very informative and helpful article.

Reply

umesh sharma February 20, 2014 at 12:53 AM

Thanks Gaurav.

Anonymous March 11, 2014 at 3:22 PM

Nicely explain all of them...Really appreciated.

Reply

umesh sharma March 11, 2014 at 11:01 PM

Thanks Dear.


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umesh sharma March 11, 2014 at 11:01 PM

Thanks Dear.

Anonymous April 15, 2014 at 4:40 AM

Dear Umesh ,

I really appreciate your effort for e xplanation of AWR.

Many thanks for sharing this article.

RegardsGoulay

Oracle DBA

Reply

umesh sharma April 15, 2014 at 5:07 AM

Welcome friend.

Ravi Suvvari July 6, 2014 at 12:27 AM

Very informative

small typo

10. SQL Ordered by CUP Time needs to be read as 10. SQL Ordered by CPU Time

Reply

Ravi Suvvari July 6, 2014 at 12:38 AM

SQL execute elapsed time is taking 89% of DB should be SQL execute elapsed time is taking 98%

of DB (looks like typo)

Reply

satya svits29 August 30, 2014 at 12:55 PM

awesome article keep them coming

Reply

Anonymous August 31, 2014 at 5:48 AM

thanks

Reply

Venkat September 12, 2014 at 5:49 AM

Superb article.. helped me in understanding the awr report checks.. Great job..

Thanks

Reply

Anonymous November 25, 2014 at 8:02 AM

very helpful....thanks for sharing!

Reply

Anonymous December 4, 2014 at 12:23 PM

you need to fix this

SQL Ordered by CUP Time

SQL Ordered by CPU Time

Reply

Anonymous December 23, 2014 at 2:08 AM

This report has been taken when user sessions are active for long time. Please tell me what is

sbtwrite2.

Top 5 Timed Events Avg %Total

~~~~~~~~~~~~~~~~~~ wait Call

Event Waits Time (s) (ms) Time Wait Class

------------------------------ ------------ ----------- ------ ------ ----------

Backup: sbtwrite2 40,575 801 20 207.2 Administra

RMAN backup & recovery I/O 69,380 588 8 152.2 System I/O

CPU time 318 82.3

Backup: sbtclose2 22 113 5131 29.2 Administra

control file parallel write 51,693 97 2 25.0 System I/O

Reply

Anonymous January 26, 2015 at 3:08 AM

In the #6 you mention about "Concurrency" as serious problem - could you give any example? What

does it mean concurency?

Reply

Mohamed February 12, 2015 at 5:36 AM

As in real life, concurrency means to client wants to access to the same object

simultaneously. Lock is the solution but could be an issue, when it is not released or take

a lof of time to release the object....


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Reply

simultaneously. Lock is the solution but could be an issue, when it is not released or take

a lof of time to release the object....

vikas jain April 21, 2015 at 2:57 AM

Very Nice article - appreciated

Can you please explain:

#6 you mention about "Concurrency" as serious problem - could you give any example? What does

it mean concurrency?

-Vikas

Reply

Vincent April 21, 2015 at 11:19 AM

Thank you.

In the first part, I don't understand why you use "cores" and not "cpus". And I don't know what

appends if the cpu_counts parameters is setted less?

Reply

Lakshminarayana Hs September 7, 2015 at 6:37 AM

It is the nice document...It is better if you give recomendation on below issue.

1."% Non-Parse CPU% is just 50%

2.recomended value for cursor_sharing

thanks

Lakshminarayan

Reply

Lakshminarayana Hs September 7, 2015 at 6:37 AM

It is the nice document...It is better if you give recomendation on below issue.

1."% Non-Parse CPU% is just 50%

2.recomended value for cursor_sharing

thanks

Lakshminarayan

Reply

Anonymous September 14, 2015 at 12:08 PM

Many Thanks for sharing this, very much informative and useful

Reply

Chandra Reddy October 4, 2015 at 6:28 AM

Superb article for Beginners.

Reply


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