RE: Inconsistent file IO times on AWR report
- From: "Stephens, Chris" <Chris.Stephens@xxxxxxx>
- To: "nkodner@xxxxxxxxx" <nkodner@xxxxxxxxx>, oracle-l-freelists <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 4 May 2010 08:11:13 -0500
Since blocks from the heaviest hit tablespace are more likely to be in the
os-cache, that would account for Oracle thinking blocks read from that
tablespace are faster. I guess that assumes you aren't using direct-io.
Chris
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Neil Kodner
Sent: Tuesday, May 04, 2010 7:35 AM
To: oracle-l-freelists; Neil Kodner
Subject: Inconsistent file IO times on AWR report
I'm trying to get to the bottom of some performance issues and one of the
things that stumps me is that my AWR reports show wildly inconsistent read
times for my tablespaces. The heaviest-hit tablespace consistently shows an
average read time of .59ms. The others range from 13 to 25ms in avg read time.
I dont find anything obvious when comparing matviews_index and matviews_data
to the rest of the tablespaces when looking in dba_tablespaces.
Given that all of the tablespaces are on the same hardware device and mount
points, I would expect the average read times to be somewhat similar across the
board. Is this an invalid assumption?
The tablespace and file details from awr can be found at http://goo.gl/CTaO
I'll update the document with additional information as requested.
Thanks,
Neil
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