Re: see higher CPU usage after increase SGA

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Wed, 9 Jun 2004 16:17:22 +0100
Message-ID: <023d01c44e34$dcee7ee0$7102a8c0@Primary>

One note in line

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: "zhu chao" <chao_ping_at_vip.163.com>

: There was a HUGE SQL(which used 30% of total system buffer_gets
: according to statspack report). I changed the SQL, and later it used less
: than 0.5% of total system buffer_gets(it just dissappear from statspack
: report), but system CPU usage just drop by less than 5% from statspack
: report(compare the CPU used by this session before/after change)!.
:

Bear in mind that not all visits to buffered blocks are performed as 'buffer gets' - some are performed as 'buffer is pinned count'. Also, if you visit a block to collect one row through an index, you may do a few comparisons to acquire and confirm that row. If you visit the block through a table scan, you have to check every row in the block to identify the one row - and the comparisons may use a lot of CPU.

Please see the official ORACLE-L FAQ: http://www.orafaq.com

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Received on Wed Jun 09 2004 - 10:14:14 CDT