Re: see higher CPU usage after increase SGA
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Wed, 9 Jun 2004 16:17:22 +0100
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
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----- Original Message -----
From: "zhu chao" <chao_ping@xxxxxxxxxxx>
: 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.
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