RE: Sync redo log waits
Date: Tue, 19 Feb 2013 12:23:04 -0600
Message-ID: <F05D8DF1FB25F44085DB74CB916678E885823B7D41_at_NADCWPMSGCMS10.hca.corpad.net>
Also see note "How To Maintain and/or Add Redo Logs [ID 602066.1]" (section B. on determing good redo log size)
Chris
-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Paul Houghton
Sent: Tuesday, February 19, 2013 11:49 AM
To: saad4u_at_gmail.com; oracle-l_at_freelists.org
Subject: RE: Sync redo log waits
Hi
According to a number of oracle support notes, e.g. 147468.1 performance will be impacted if log switches more often than about once every 15 minutes. That note specifically says that performance will be impacted by switching once every 3 minutes, which is around what you are doing.
So yes, you should increase the size of the redo logs to 4.5 - 6 times their current size unless you are sure you can reduce the number of switches by reducing the workload.
We have a cron job which switches the log file every 15 minutes to ensure the standby is up to date, though I am not sure if this is needed any more (11.2).
You may be able to talk with the application people to get them to spread the load. Sometimes you get a trendy time to start a batch process (say 2am) and everyone starts their process at this time, though I can't see a pattern in the data you posted. Does the application keep some kind of log or audit of what it was doing which you could consult to find out what was being run, or use AWR reports if you have tuning pack, or even statspack and tune that area of the application or move it to a quieter time?
Hope this helps
PaulH
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Received on Tue Feb 19 2013 - 19:23:04 CET