RE: Important: Oracle processes taking lots of CPU

Both the time spent in user mode (%usr) spinning for a latch and the = time
spent in kernel mode (%sys) contribute to the c statistic shown in = extended
SQL trace files.

If your system is enduring a lot of preemptions (context switching), you = can
also detect that in your extended SQL trace data by noticing that a significant proportion of your total response time is unaccounted for. = You
can detect unaccounted-for time in your extended SQL trace data, but I = don't
think there's any way to detect it Oracle's V$/X$ data.

Cary Millsap
Hotsos Enterprises, Ltd.
http://www.hotsos.com
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-----Original Message-----
From: oracle-l-bounce_at_freelists.org =
[mailto:oracle-l-bounce_at_freelists.org]
On Behalf Of John Kanagaraj
Sent: Wednesday, November 24, 2004 1:13 PM To: 'New DBA'; ORACLE-L_at_freelists.org
Subject: RE: Important: Oracle processes taking lots of CPU

Hi New DBA,

>As I understand, the CPU is used while performing
>LIOs, doing calculation, sorts or while spinning for
>the latches. My understanding might be wrong! Since
>there aren't enough LIOs or complex calculations
>involved I thought that spinning for latches might be
>causing excessive CPU.=20

Spinning does cause CPU issues. I believe that if you have many = processes
and comparatively lesser number of processors, then you might have a lot = of
CPU consumption that is unaccounted for as cycles used for process = context
switching is not accounted in oracle. You will have to then look at 'sar = -u'
( look for high %sys), 'sar -q' (look for high run queue size and = occupancy)
and 'sar -w' (look for excessive process switches).

Let us know if this helps,
John Kanagaraj <><
DB Soft Inc
Phone: 408-970-7002 (W)

http://tahiti.oracle.com - Manuals for DBAs (English only) http://www.bibleserver.com - Manual for Life (in English, Deutsch, = French,
Italian, Spanish, Portugese, Turkish,...)

• The opinions and facts contained in this message are entirely mine = and do not reflect those of my employer or customers ** -- http://www.freelists.org/webpage/oracle-l

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