Re: Instance Efficiency Percentages - Library Hit %: in AWR
Date: Wed, 4 Apr 2012 13:56:11 -0700 (PDT)
Message-ID: <1333572971.42915.YahooMailNeo_at_web83602.mail.sp1.yahoo.com>
Hi Sreejith,
Although I can't help you directly on the SQL you requested, but once you do start trend this phenomenon, here are a few things that will provide food for investigation and thought:
- What the are Top 5 Wait Events when this Instance Efficiency Percentage is low?
- Which SQL statements are being negatively affected by the Top 5 Wait Events? By how much?
- Is there a problem on your database for the period of the snapshot(s)?
- How does this snapshot's workload compare to a baseline snapshot?
- Is there evidence of some sort of abnormal application workload?
- Did you have more parsing than normal?
- What caused the increased parsing (if applicable)?
- Or was the increased parsing due to automatic memory management stealing from the shared pool to feed the db buffer cache in response to an increase I/O load?
Cheers,
Gaja
Gaja Krishna Vaidyanatha,
CEO & Founder, DBPerfMan LLC
http://www.dbperfman.com
http://www.dbcloudman.com
Phone - +1-650-743-6060
http://www.linkedin.com/in/gajakrishnavaidyanathaCo-author:Oracle Insights:Tales of the Oak Table - http://www.apress.com/book/bookDisplay.html?bID14
Co-author:Oracle Performance Tuning 101 - http://www.amazon.com/gp/reader/0072131454/ref=sib_dp_pt/102-6130796-4625766
Enabling Cloud Deployment & Management for Oracle Databases
From: Sreejith S Nair <Sreejith.Sreekantan_at_ibsplc.com> To: oracle-l_at_freelists.org
Sent: Wednesday, April 4, 2012 2:39 AM
Subject: Instance Efficiency Percentages - Library Hit %: in AWR
Hi Friends,
In AWR under Instance Efficiency Percentages we see a Library Hit % and we
find it very low for one snapshot. I would like to know the trend for few
more days available in AWR snapshots
(dba_hist_snapshot,DBA_HIST_LIBRARYCACHE) using SQL Query.
Can some one please help with how this % is being calculated. What SQL can I use to calculate this ? May be for a range of snapshot. Thanks in Advance.
11.2.0.2.0 on Solairs 10 .
With Regards,
Sreejith
--
Sreejith S Nair
Associate Systems Architect | AOS DBA Team
IBS Software Services Private Ltd.
2nd Floor, IBS Campus, Technopark Campus, Trivandrum - 695 581, Kerala,
India
((Direct) +91 471 661 4707 ) +91 808 648 5523
*sreejith.sreekantan_at_ibsplc.com
8 www.ibsplc.com
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Received on Wed Apr 04 2012 - 15:56:11 CDT