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Re: Buffer Cache Hit Ratio Discrepency

From: kyle hailey <nospam_khailey_at_fr.oracle.com>
Date: 1997/11/25
Message-ID: <347ADDD6.6891@fr.oracle.com>#1/1

The cache buffer ratio is a v6 tuning construct. On v7 if you want to find out how much users are waiting on reads of buffers into the SGA, then the wait events as seen in the utlbstat/utlestat are the wait to go. There are two kinds of waits on the buffer reads, 'db file sequential read' and 'db file scattered read'. the scattered is bassically a full table scan, sequential in general is a lookup by rowid id, which usually comes from an index. If have a horrible cache buffer hit ratio and no db file waits you are ok (this can happen with unix buffer caching) or if you have a beautiful cache buffer hit ratio but huge waits on db file reads there is a problem. The ratio is irrelevant.

        Just my 2 cents on the subject.

Best
Kyle Hailey
Oracle Support France

[ The statements and opinions expressed here are my own and do not necessarily represent those of Oracle Corporation. ] Received on Tue Nov 25 1997 - 00:00:00 CST

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