10 Steps To Analyze Awr Report In Oracle 2s656m

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

1 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

10 Steps to Analyze AWR Report in Oracle 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 for Automatically 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. Collect Multiple AWR Reports: It's always good to have two AWR Reports, one for good 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 resolve performace 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 for long 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 database and instance and and database version with the Database having performance issue.This report also show RAC=YES if it's an RAC database.

2. Host Configuration: This will give you name, platform CUP, socket and RAM etc. Important thing to notice is number of cores into the system. In this example there are 12 CUP's in Cores.

3. Snap Shot Detail: This are the detail about snap shot taken, Snap start time and end time. Difference between them is as "Elapsed". Here is a new term "DB Time"

DB Time= session time spent in database. DB Time= U Time + Non IDLE wait time. You can find, DB time is very large as compared to 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 Cache Sizes, which is just detail about SGA components.

4. Load Profile: Here are few important stats for a DBA to look into. Fist is "DB U(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 U.

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

2 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

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 U.

So, if "DB U(s)" per second in this report > cores in (Host Configuration (#2)). means env is U bound and either need more U'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 U bound. In this case, machine has 12 cores and DB U(s) per second is 6.8. So, this is not a U bound case. Next stat to look at are Parses and 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 like cursor_sharing and application level for bind variables etc.

5. Instance Efficiency Percentages: In these statistics, you have to look at "% Non-Parse U". If this value is near 100% means most of the U 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 for wait class if wait class is 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 Avg Wait (ms). If Time(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 U = 64% DB time. Taking resource by DB CUP is a normal situation. Let's take an example, In which event is "log file switch (checkpoint incomplete) " which has high waits, huge Time (s) and large values in Avg Wait (ms) and wait class is configuration. So, here you have to investigate and resolve log file switch (checkpoint incomplete). Host U, Instance U and Memory Statistics 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.

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

3 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

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, or sys % and indeed this will led to low idle %. Investigate what is causing this. OS Watcher is the tool which 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 by Elapsed time into reported time interval.

In this report, look for query has low executions and high Elapsed time per Exec (s) and this query could be a candidate for 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 U taken by the query i.e. queries causing high load on the system. The top few queries could be the candidate query for optimization.

From above stat, look for queries using highest U Times, If a query shows executions 0, 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 commonly used stats for any performance related information. Please share you view about this article, Does it helps you to understand, How to analyze AWR Report. You might also like: Oracle Advanced Compression Licensing Manual Upgrade Database from Oracle 10.2.0.4 to Oracle 11.2.0.2 What is OS Watcher Utility and How to use it for Database Troubleshooting ? Linkwithin

Labels: Performance Tuning

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

4 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

Labels: Performance Tuning

Profile

Performance Review

Digital picture frame reviews

Website Developers Free web design tutorials

45 comments: Anonymous July 2, 2013 at 10:35 AM Nice article, me also working in oracle side as a Tech Arch. Keep n touch Thanks Vijay Bangalore [email protected] Reply Replies 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.

Reply

Rishiraj Chockraborty September 2, 2013 at 11:37 PM Very Good article....thanks for sharing this.... Reply Replies umesh sharma

September 4, 2013 at 7:33 AM

Thanks for your complement.

Reply

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 DBA [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 Replies umesh sharma

October 28, 2013 at 9:23 AM

Thanks Feroz

Reply

Pa December 3, 2013 at 3:29 AM Thanks for Sharing the document, its good analysis of AWR Report.

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

5 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

Pa December 3, 2013 at 3:29 AM Thanks for Sharing the document, its good analysis of AWR Report. Thanks & Regards, Pa Jr. Oracle DBA [email protected] Reply

Pa December 3, 2013 at 3:31 AM 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 Replies umesh sharma

December 10, 2013 at 2:09 AM

Thanks friend.

Reply

Anonymous January 3, 2014 at 3:59 AM Really this article helped me alot.Thanks Umesh Reply Replies umesh sharma

January 3, 2014 at 4:07 AM

Thanks friend.

Reply

Sharv Gupta January 17, 2014 at 11:20 PM Thanks a lot Umesh for this useful article. Reply Replies umesh sharma

January 19, 2014 at 8:58 AM

Thanks dear.

Reply

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 Replies umesh sharma

February 20, 2014 at 12:53 AM

Thanks Gaurav.

Reply

Anonymous March 11, 2014 at 3:22 PM Nicely explain all of them...Really appreciated. Reply Replies umesh sharma

March 11, 2014 at 11:01 PM

Thanks Dear.

Reply

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

6 de 7

umesh sharma

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

March 11, 2014 at 11:01 PM

Thanks Dear.

Reply

Anonymous April 15, 2014 at 4:40 AM Dear Umesh , I really appreciate your effort for explanation of AWR. Many thanks for sharing this article. Regards Goulay Oracle DBA Reply Replies umesh sharma

April 15, 2014 at 5:07 AM

Welcome friend.

Reply

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 U 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 U Time Reply

Anonymous December 23, 2014 at 2:08 AM This report has been taken when 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 istra RMAN backup & recovery I/O 69,380 588 8 152.2 System I/O U time 318 82.3 Backup: sbtclose2 22 113 5131 29.2 istra 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 Replies 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....

Reply

12/10/2015 0:43

DBAs-Oracle.com: 10 Steps to Analyze AWR Report in Oracle

7 de 7

http://www.dbas-oracle.com/2013/05/10-steps-to-analyze-awr-report-i...

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....

Reply

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 "us". And I don't know what appends if the u_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 U% 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 U% 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

12/10/2015 0:43