RE: Average physical read times for AIX & SAN

Daniel,
I am sorry to be so slow to respond to this, it was caught by my junk filter and only emerged today.

Reading this, at first I thought that you were internal to my company. We have the same configuration and here are a few gem lines from sid_lgwr_123.trc

Warning: log write time 620ms, size 2501KB *** 2008-10-08 18:13:50.581
Warning: log write time 2000ms, size 9435KB *** 2008-10-08 18:13:51.779
Warning: log write time 870ms, size 4072KB *** 2008-10-08 18:13:53.07

I have seen these write times also when less than 1KB was being written. My winner warning so far was for 23 seconds! If you have learned anything about this issue, I would LOVE to hear it. Thanks a million,
Claudia Zeiler

-----Original Message-----

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Daniel Fink Sent: Wednesday, September 24, 2008 9:18 AM To: oracle-l
Subject: Average physical read times

In a recent optimization effort, I found what I think are high physical read times. For example, a single block read was averaging 11 milliseconds with a max of over 1 second (tkprof output). For this session, single block reads consumed over 80% of the response time, so this is of concern.

We are running Oracle 10gr1 on AIX with an IBM storage array (shared amongst many servers). I suspect there is some optimization that can be done at the storage array level. If 11 milliseconds is well above average, this will help in engaging that team in the process.

For those of you running statspack. AWR or other monitoring tools, what are the average single block read times you are encountering on a good system? If you are running on an IBM storage array, have you found any specific issues/fixes?

Regards,
Daniel Fink

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Daniel Fink

OptimalDBA.com - Oracle Performance, Diagnosis, Data Recovery and Training

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http://www.freelists.org/webpage/oracle-l Received on Thu Oct 09 2008 - 13:29:19 CDT