Re: DB CPU is much lower than CPU Time Reported by TOP SQL consumers
- From: Karl Arao <karlarao@xxxxxxxxx>
- To: exriscer@xxxxxxxxx
- Date: Tue, 13 Nov 2012 15:13:57 -0600
Can you post the Top 5 timed events and Begin,End,Elapsed, DB Time sections
of your AWR?
most likely this is a CPU starvation related.. In AWR/Statspack, that
"Captured SQL.. CPU" section is being pulled from sum(cpu_time_delta) of
dba_hist_sqlstat and divided by 'DB CPU' by the time model which only
accounts for the "real CPU cycles" which gives you a lower value for the
denominator since most of the CPU time is spent on run queue and not
accounted
But the beauty about the time model is when database foreground goes from
on-CPU to on-run queue to on-CPU the time spent on run queue will be added
to 'DB Time' but not visible in 'DB CPU' or in any wait event... and that's
what you see as "CPU wait" as a light green color in the OEM.
you can use the following to compute for CPU wait..
CPU Wait = DB Time ? ( sum(events) + DB CPU )
You should be able to account for this even if you are using just the
Statspack this link contains some background http://goo.gl/trwKp
--
Karl Arao
karlarao.wordpress.com
karlarao.tiddlyspot.com
twitter.com/karlarao
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