Re: CPU Time calculation in AWR Reports

Thanks for your valuable and precise suggestion, Tanel.

In a nutshell, this is what AWR does:

   select 'CPU' , (e.value-b.value)/1000000 time
     from dba_hist_sys_time_model b, dba_hist_sys_time_model e
    where e.snap_id         = :v_eid
      and b.snap_id         = :v_bid
      and e.stat_name       = 'DB CPU'
      and b.stat_name       = 'DB CPU';


Best regards,
Cerri




2007/11/1, Tanel Poder <tanel.poder.003@xxxxxxx>:
> Well you can trace the awrrpt run...
>
> I suspect (but don't know for sure) that AWR uses DBA_HIST_SYS_TIME_MODEL
> for its CPU info... V$SYS_TIME_MODEL CPU values can differ from V$SYSSTAT
> ones...
>
> SQL> select
>  2     a.value/1000000 time_model_seconds,
>  3     b.value/10000   sysstat_seconds,
>  4     a.value/1000000 - b.value/10000 missing_seconds
>  5  from
>  6     v$sys_time_model a,
>  7     v$sysstat b
>  8  where
>  9     a.stat_name = 'DB CPU'
>  10  and b.name = 'CPU used by this session'
>  11  /
>
> TIME_MODEL_SECONDS SYSSTAT_SECONDS MISSING_SECONDS
> ------------------ --------------- ---------------
>        126.997282          4.6276      122.369682
>
>
> --
> Regards,
> Tanel Poder
> http://blog.tanelpoder.com
>
>
> > -----Original Message-----
> > From: oracle-l-bounce@xxxxxxxxxxxxx
> > [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Luis
> > Fernando Cerri
> > Sent: Thursday, November 01, 2007 23:20
> > To: oracle-l@xxxxxxxxxxxxx
> > Subject: CPU Time calculation in AWR Reports
> >
> > Hello, list.
> >
> > At Statspack age, 'CPU Time' value in section 'Top 5 Timed
> > Events' was calculated as the difference of 'CPU used by this
> > session' values between two snapshots:
> >
> >                        select 'CPU' , (e.value-b.value)/100 time
> >                          from stats$sysstat b, stats$sysstat e
> >                         where e.snap_id         = :v_eid
> >                           and b.snap_id         = :v_bid
> >                           and e.name            = 'CPU used
> > by this session'
> >                           and b.name            = 'CPU used
> > by this session';
> >
> >
>
>
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