RE: Physical Reads and Writes
From: Allen, Brandon <Brandon.Allen_at_OneNeck.com>
Date: Fri, 28 Aug 2009 13:13:33 -0700
Message-ID: <64BAF54438380142A0BF94A23224A31E1129528AA8_at_ONEWS06.oneneck.corp>
Maybe unlikely, but not impossible - just because the database is 300GB doesn't mean that users weren't only querying a small portion of it (e.g. just the most current data) at the time when you were running the sar command. I also work with several DBs in that same size range, but most of it is historical and probably less than 5% of the blocks are used on a regular basis - that's how we get by with just a 3GB buffer cache on a 300GB database. I'm not trying to say that all your blocks are cached, just saying that I wouldn't ignore it as a real possibility so I'd recommend digging deeper to see if it's actually the case or not.
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Date: Fri, 28 Aug 2009 13:13:33 -0700
Message-ID: <64BAF54438380142A0BF94A23224A31E1129528AA8_at_ONEWS06.oneneck.corp>
Maybe unlikely, but not impossible - just because the database is 300GB doesn't mean that users weren't only querying a small portion of it (e.g. just the most current data) at the time when you were running the sar command. I also work with several DBs in that same size range, but most of it is historical and probably less than 5% of the blocks are used on a regular basis - that's how we get by with just a 3GB buffer cache on a 300GB database. I'm not trying to say that all your blocks are cached, just saying that I wouldn't ignore it as a real possibility so I'd recommend digging deeper to see if it's actually the case or not.
Regards,
Brandon
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-- http://www.freelists.org/webpage/oracle-lReceived on Fri Aug 28 2009 - 15:13:33 CDT