The best CPU usage measurement in Oracle: BUFFER_GETS or CPU_TIME?

From: <J.Velikanovs_at_alise.lv>
Date: Fri, 18 Jun 2004 10:47:54 +0300
Message-ID: <OF92211738.772B1626-ONC2256EB7.002ABED1-C2256EB7.002B7C34@alise.lv>

My regards to all members,
Just would like to know your opinion.
Since 9i (suppose 9.2) we have CPU_TIME column in the V$SQL view.

I wonder which figure is the best measurement of CPU usage BUFFER_GETS or CPU_TIME?

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Lets imagine I have system with CPU bottleneck (can see height “load average” from OS) for a 1-3 ours. No particular long sessions have been executed. It is seams mainly OLTP system. Parse CPU usage not the issue.

I would like to identify TOP CPU consumers. As we all know I the V$SQL is the best information source in this case.

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I wonder which figure is the best measurement of CPU usage: BUFFER_GETS or CPU_TIME? Statspack report, as well as Anjo Kolk www.oraperf.com recommending to look on BUFFER_GETS not to CPU_TIME. Is it just tradition or there are some arguments not to look on CPU_TIME as main CPU usage indicator.

One reason I can imagine why CPU_TIME better indicator then BUFFER_GETS is sorting. I can imagine that BUFFER_GETS not taking in account CPU spent to sorting staff. Then from CPU usage perspective better indicator is CPU_TIME.
Please correct me if I am wrong.

Thanks in advance,
Jurijs

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Received on Fri Jun 18 2004 - 02:51:44 CDT