AWR snapshot question

Hi:
I create a snapshot manually use dbms_workload_repository.create_snaphost at 15:51 , then the 16:00 snapshot by system is not generated.
so have any method can force system execute snapshot on the hour，even I manually snap?
Edited by: tomykety on May 29, 2013 2:00 AM

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Please post the output of DBA_HIST_SNAPSHOT view,this will show what shapshot you have with their begin and end time.
By default AWR snapshot are taken every hour.

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AWR Snapshots Required When Database is in Restricted Mode

We are planning to run some processes, but want the database to be in restricted mode to keep "normal" users out.
But we also need to monitor performance on the system during that. Normally however, scheduled jobs such as this don't run in restricted mode.
Does anyone know of any way of still (preferably automatically) running the AWR snapshots when the database (Version 10.1.0.5) is in restrict mode.
I know this may be a little off-topic for this forum, but it was the nearest I could find.
Any information gratefully received.

Hi,
Unfortunately this is not possible in version 10.1 .
In 10.2.0.4 (when it is released) and 11g it is possible to allow this using the ALLOW_RUNS_IN_RESTRICTED_MODE boolean job attribute.
In prior releases no jobs will run when the database is in restricted mode.
Thanks,
Ravi.

AWR snapshot not generatedand how to compare statistics with a baseline

01. AWR snapshot not being generated even after setting looks fine
02. compare a captured set of statistics with a baseline.
i m not much clear on this, please help as i have this requirement at hand.
Thanks a lot in advance.

01.
SQL> show parameter statis
NAME TYPE VALUE
statistics_level string TYPICAL
I explicitly run and did cntl^C as it looks running endless... (waited almost 2-3 hours).
SQL> exec dbms_workload_repository.create_snapshot;
^CBEGIN dbms_workload_repository.create_snapshot; END;
ERROR at line 1:
ORA-01013: user requested cancel of current operation
looks like job_name is enabled.
GATHER_STATS_JOB TRUE WEEKNIGHT_WINDOW
freq=daily;byday=MON,TUE,WED,THU,FRI;byhour=22;byminute=0; bysecond=0
GATHER_STATS_JOB TRUE WEEKEND_WINDOW
freq=daily;byday=SAT;byhour=0;byminute=0;bysecond=0
anything else can be checked, i dont have access to OEM..must be done at SQL prompt.
02. thanks for info. i understand.. how do we compare set of snapshots with baseline(which is actually pair/range of snapshot kept for further comparison)
no access to OEM. must be done at SQL prompt.
please help in both. thanks ...

One of RAC instance doesnt generate awr snapshot

Hi,
I have a problem about awr snapshots. One of RAC instance doesn t generate awr snapshot.
When I look over alert.log. I couldn t see any error message
is there anybody to have idea about this issue?
OS Level HP-UX ITANIUM 11.23
DB version Oracle RAC 10.2.0.4
Regards,

hi JohnWatson
thanks for your reply
I have run dbms_workload_respository.create_snapshot on both of two nodes.it has finished succesfully and I saw this record in the dba_hist_snapshot view
I haven t seen any error record in alert log and there isn t any trace file occured.
In other words, when I run this create snapshot command in working node, the snapshot of other node doesn t generate in the dba_hist_snapshot view
but when I run this command broken node (so it doesn t generate awr snapshot) manually , other node isn t triggered to generate awr snapshot,
SQL> exec dbms_workload_repository.create_snapshot ;
PL/SQL procedure successfully completed.
select instance_number,begin_interval_time,end_interval_time from dba_hist_snapshot where snap_id in(40274);
INSTANCE_NUMBER BEGIN_INTERVAL_TIME END_INTERVAL_TIME
1 16-JAN-13 01.00.54.450 AM 18-JAN-13 03.51.19.951 PM
2 18-JAN-13 03.43.02.430 PM 18-JAN-13 03.51.20.103 PM
regards,
Edited by: dataseven on 18.Oca.2013 06:19

Performance impact after changing the awr snapshot timing from 1 hour to 15 minuts.

want to know performance impact after changing the AWR snapshot timing from 1 hour to 15 minutes.

Hi,
1) typically performance impact is negligible
2) we have no way of knowing whether or system fits into the definition of "typical"
3) the best way would be to do that on a test system and measure the impact
4) I would be concerned more about SYSAUX growth than performance impact -- you need to make sure that you won't run out of space because of x4 more frequent snapshots
Best regards,
Nikolay

Why no AWR snapshots for my query since I fixed the baseline plan?

So I've got a query for which I've fixed the baseline plan and since doing so I no longer see any AWR snapshots for that sql_id in
DBA_HIST_SNAPSHOT
Edited by: steffi on Feb 24, 2011 8:07 PM

Any chance fix resulted in better performance? So fast that is parses, executes and ages out before snapshots can catch it?

Modify the AWR snapshot time interval

Hi,
on 10g R2 how to Modify the AWR snapshot time interval to two hours ?
Thanks.

Hi,
Please see the below link to modify AWR snapshot time interval through command prompt and EM Datbase/Grid Control
http://www.dba-oracle.com/art_dbazine_freeman_database_advisors_p1.htm
Hope this helps.
Regards
Satishbabu Gunukula
http://oracleracexpert.blogspot.com
[Click here to lean Delete Archive logs using RMAN|http://oracleracexpert.blogspot.com/2009/08/delete-archive-logs-using-rman.html]

Keep AWR snapshots even after a recycle

Hi,
Everytime I bounce my DB, I loose all my snaphshots from my AWR since the last time the DB was bounced? I know how to change most of the settings for AWR but is there a way to prevent it from purging all the snapshots during a shutdown of a DB?

You are true but how much we loose here that's the real issue. Let's take some scenario
1. In one hour window you loose 15-20 minutes it's fine isn't it. Still you can get atleast for 40 minutes of AWR and is well enough to track performance.
2. Let's say instance dies at starting of 1 hr windows lets say at 10 minutes. We can look some backward data and find out details.
3. Or just reduce retention
4. Or SELECT * FROM TABLE(dbms_workload_repository.ash_report_txt(dbid, , start date, end date));
But this all depends what you are looking for performance or just finding some past data.

DB CPU event in top 5 of AWR report question

The top 5 foreground event in my AWR report is as follows. I am trying to understand if my db(system) is CPU bound.The elapsed time is 30 minutes and DB time is 675 in the load profile section. There are 32 cpus. The available CPU is 30*60*32 => 57600. The DB CPU below is 35227. This is about 61 %. At what percentage of DB CPU do I consider my system is CPU bound ?. Also I want to make sure the method I arrived at this is correct or not. Please help. Event Waits Time(s) Avg wait (ms) % DB time Wait Class DB CPU 35,277 87.12 DBMS_LDAP: LDAP operation 3,683 10,061 366 9.1 Other db file sequential read 233,584 933 4 2.3 User I/O read by other session 41,686 190 5 0.47 User I/O log file sync 70,932 166 2 0.41 Commit

Why does the top 5 foreground indicate 87 % below the % DB Time column ? While my calculation shows 61 %, Which is correct for the interpretation if the system is CPU bound. The 2 lines of top 5 events are as follows
Event
Waits
Time(s)
Avg wait (ms)
% DB time
Wait Class
DB CPU
35,277
87.12

Zfs snapshot question

Hi guys,
I will really appreciate it if someone can answer this for me.
I do understand that you can use snapshots to back up file systems. But they also use up pool space when their file systems grow.
So, is it necessary to create zfs snapshots even when you already have a full system back up in place?
Thank you very much for your kind explanation.
Arrey

985798 wrote:
So, is it necessary to create zfs snapshots even when you already have a full system back up in place? Nobody will force you to create or keep snapshots and if you are happy with taking "classic" backups then there may be no need for additional snapshots. And since snapshots will also take up space in your pool, it is usually a good idea to keep them only for a short period and delete them periodically. I like to use snapshots for two purposes:
- create a snapshot, then write that snaptshot to take and destroy it afterwards. that way, you can guarantee that this tape backup is consistent
- create snapshot at regular intervals and keep them around for a few days so that if I need to restore a file from just a day ago I don't have to go back to tapes but can rather fetch it from the snapshot. So that would be in addition to regular backups
cheers
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Acquire snapshot question

hi,
first of all many thanks for this great tool.
i want to acquire snapshot directly form my nw04s server, how can i activate this function ?
Thank you

Hi Didier,
as nw04s runs on jdk1.4.2, the easiest way to acquire a heap dump is on Ctrl-Break. To use this option you need to configure the following Java VM parameter:
-XX:+HeapDumpOnCtrlBreak.
The heap dump will be written to the working directory of the server, e.g. /usr/sap/<SID>/J<instance>/j2ee/cluster/server<node>/
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AWR on a RAC Environment

Hello Knowledgeable Guys of Oracle Forums...
Finally, our management has bought a license for AWR (after years of using the system!!!) because the database performance has been degrading for quite a while....goodbye to statspack!
I have a question on AWR collection on RAC..
We have a 5 Node RAC Cluster working on Oracle 10g R2 on Linux 5.1...
I would like to know:
1. How to collect AWR snapshots in a RAC environment? Do I need to collect AWR per node (per instance)?
2. Is there a way to collect AWR for the entire RAC cluster (Node 1 to Node 5)?
3. What is the proper way (best way) to collect AWR reports in our 5-node RAC?
4. How does AWR work on RAC?
Any sample blogsites...or sample actual AWR collection that you use in your system...
Thank you

Hi
1. How to collect AWR snapshots in a RAC environment? Do I need to collect AWR per node (per instance)?
A: No. You should collect it at DATABASE level
2. Is there a way to collect AWR for the entire RAC cluster (Node 1 to Node 5)?
A: Yes. You can simple generate an html or text report for your RAC environment (eg: AWR report)
3. What is the proper way (best way) to collect AWR reports in our 5-node RAC?
A: You can use the snapshots to compare periods, or reports
4. How does AWR work on RAC?
A: AWR snapshots are collect at database level, and you can use this snapshot to generate your AWR reports.
You can also take snapshot in a given moment and use them to reports.
Exeamples:
TO CHANGE AWR SNAPSHOTS INTERVAL
* retention /interval in seconds
Exec dbms_workload_repository.modify_snapshot_settings (retention=>43200, interval=> 60);
TO TAKE A SNAPSHOT MANUALLY
execute dbms_workload_repository.create_snapshot;
TO GENERATE AWR REPORTS
@?/rdbms/admin/awrrpt.sql
Victor

Questions about Real Application Testing(RAT)

Hi All,
We have a production database running on 10gR3 on a server with local drives, while we have a Oracle 11gR2 DB running on a server with NFS mounts (using S7310 - AmberRoad) i.e. Faster and better storage.
We captured the load on 10gR3 and replayed it on 11gR2. We noticed the following:
(1) Replay is considerably slow even though Oracle11gR2 instance has a faster storage. We suspect that it may be something to do with the buffer cache / SGA because there is nothing in cache on the target (we didn't shutdown 10gR2 DB for capture) – what should we do then?
(2) To make sure that we can take the advantage of cache, we replayed the load 2nd time right after the 1st replay and everything ran to our surprise. So we are wondering how’s that possible since we did not restore the DB as we do not want to wipe off the cache (chicken and egg situation)? Does Oracle rollback the changes after the replay?
(3) Do we have to restore database on Target every time we do replay? But if we do that then we won't have anything in the SGA.
So we need your advise and also would like to know how everyone else is doing this testing?
Regards,
RJiv.

DB Replay's workload capture facility allows you to either start capture from a closed (mounted) database (capture starts upon opening the DB), or to begin capture mid-stream during normal activity. Starting capture on the production system from a closed database eliminates the divergence in performance resulting from a primed cache, as well as possible data divergence issues from open, partially-completed transactions at the time the capture started.
For many customers, it will clearly not be possible to close their database during peak periods (!!)
One way to address the cache priming issue is to start capture in production from a closed state during a low period of activity, and the allow capture to run through the peak period.
Another approach is to start capture mid-stream with the DB open and to run capture for a long period (long enough to stabilize the cache). When performing the replay, begin a new AWR snapshot after the cache has stabilized.
Your question about running the replay again after the first replay is done is confusing. Of course you will not get meaningful data from that, since replay must begin from the capture start SCN. If you run replay twice in a row without reverting the database to the capture start SCN, it will be applying meaningless changes to a database in a state that is unlike that of the original. You will be testing the data errors codepath instead of real performance.
It is typical to enable database flashback on the repay database so that it can be repeatedly reverted to the capture start SCN for testing under a variety of scenarios.
Regards,
Jeremiah Wilton
Blue Gecko, Inc.
http://www.bluegecko.net

AWR analysis for sql

Hi Gurus,
db: 10.2.0.4
Please find below an extract from awr report.
SQL ordered by Gets DB/Inst: DBPL0A1/dbpl0a12 Snaps: 32720-32721
-> Resources reported for PL/SQL code includes the resources used by all SQL
statements called by the code.
-> Total Buffer Gets: 18,026,853
-> Captured SQL account for 35.3% of Total
Buffer Gets Executions Gets per Exec %Total CPU Time (s) Elapsed Time (s) SQL Id
17,640,376 0 N/A 97.9 446.91 1930.96 5nyjrk49p9vbd
Please let me know if this sql would have affected the performance.
The number of executions is "zero" compared to Big number of "Buffer Gets" = 17,640,376. Please let me know.
Also let me know if further information is required.
Thanks.
Edited by: user12582934 on Mar 2, 2010 6:24 PM
Edited by: user12582934 on Mar 2, 2010 6:28 PM

Did you ever receive an answer to your question?
I am running some SQL from within a PL/SQL Stored Procedure. I am building the statement and then doing an EXECUTE IMMEDIATE from within the stored procedure. Here is the basic code:
sql_stmt varchar2(2000);
sql_stmt := 'ALTER index '||v_index_name||' REBUILD PARALLEL';
EXECUTE IMMEDIATE sql_stmt;
This routine is called 3 times, each time with a different value for v_index_name. I see a separate statement within the AWR Report for all 3 calls. However, “Executions” is always Zero. The SQL shows in the “SQL ordered by Elapsed Time”, “SQL ordered by CPU Time”, “SQL ordered by Reads” (where “Reads per Exec” is blank/null).
The call to the PL/SQL Stored Procedure shows in the “SQL ordered by Gets” and “SQL ordered by Reads” and in each places, shows it was executed 3 times.
The call is being made and completing within the AWR Snapshot.
So, why is Executions equal to zero and Reads per Exec blank? Is it because it is being called within a PL/SQL Stored Procedure?

Lock/dedlock info in AWR views

Helo ,
I have teoretic question? Can I find , or use AWR snapshot information to resolve ORA 04020 or another lock problems?
Thank You , Brano

Hi Brano,
AWR snapshot information to resolve ORA 04020 or another lock problems?Yes, it's amazing what is inside AWR!
http://www.dba-oracle.com/t_rac_statspack_awr_performance.htm
I have a whole book on using AWR for tuning, if you are interested:
http://www.rampant-books.com/book_2005_1_awr_proactive_tuning.htm
Hope this helps. . .
DonaldK. Burleson
Oracle Press author

AWR snapshot question

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