There is no one safe measure to pursue - buffer_gets is a good guideline - but different activities on the buffer consume different amounts of CPU - so you can legally have high CPU with relatively low buffer_gets, even buffer_gets is the most significant area of activity. Latch contention pushes up CPU - so two statements with the same number of buffer-gets may report different amounts of CPU because one of them was constantly competing for a hot latch. v$sql doesn't tell you about 'buffer is pinned' activity, which is buffer activity that doesn't require latch access, so SQL with very low buffer_gets can use very large amounts of CPU. In short - neither measure is guaranteed to be sufficiently meaningful to be the better one to monitor. Regards Jonathan Lewis http://www.jlcomp.demon.co.uk http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/seminar.html Optimising Oracle Seminar - schedule updated May 1st ----- Original Message ----- From: <J.Velikanovs@xxxxxxxx> To: <oracle-l@xxxxxxxxxxxxx> Sent: Friday, June 18, 2004 8:47 AM Subject: The best CPU usage measurement in Oracle: BUFFER_GETS or CPU_TIME? My regards to all members, Just would like to know your opinion. Since 9i (suppose 9.2) we have CPU_TIME column in the V$SQL view. I wonder which figure is the best measurement of CPU usage BUFFER_GETS or CPU_TIME? ======================================================= 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. ======================================================= 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 ---------------------------------------------------------------- Please see the official ORACLE-L FAQ: http://www.orafaq.com ---------------------------------------------------------------- To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx put 'unsubscribe' in the subject line. -- Archives are at //www.freelists.org/archives/oracle-l/ FAQ is at //www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------