CPU Time calculation in AWR Reports

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CPU Time calculation in AWR Reports

CPU Time calculation in AWR Reports

2007-11-02 - By LS Cheng

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Reply: 1 2 3

I think the difference may be because v$sysstat is refreshed after a call is
completed but in SYS_TIME_MODEL_CPU it gets refreshed every 3 seconds

Thanks

--
LSC

On Nov 1, 2007 6:10 PM, Tanel Poder <tanel.poder.003@(protected)> wrote:

> 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@(protected)
> > [mailto:oracle-l-bounce@(protected)] On Behalf Of Luis
> > Fernando Cerri
> > Sent: Thursday, November 01, 2007 23:20
> > To: oracle-l@(protected)
> > 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';
> >
> >
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

I think the difference may be because v$sysstat is refreshed after a call is
completed but in SYS_TIME_MODEL_CPU it gets refreshed every 3 seconds 
 Thanks -- LSC <div class="gmail_quote">On Nov 1, 2007 6:10
PM, Tanel Poder <
<a href="mailto:tanel.poder.003@(protected)">tanel.poder.003@(protected)</a>> wrote:
 <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204,
204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">Well you can trace the
awrrpt run...
 I suspect (but don't know for sure) that AWR uses DBA_HIST_SYS_TIME
_MODEL for its CPU info... V$SYS_TIME_MODEL CPU values can differ from V
$SYSSTAT ones... SQL> select  2     a.value
/1000000 time_model_seconds,
  3     b.value/10000   sysstat_seconds,  4
    a.value/1000000 - b.value/10000 missing_seconds  5 &nbsp
;from  6     v$sys_time_model a,  7     v
$sysstat b  8  where  9     a.stat_name = &#39
;DB CPU'
  10  and <a href="http://b.name" target="_blank">b.name</a> = &
#39;CPU used by this session'  11  / TIME_MODEL_SECONDS
SYSSTAT_SECONDS MISSING_SECONDS -- ---- ---- ----- -- ---- ---- -- -- ------
-- ---
        126.997282          4
.6276      122.369682 -- Regards, Tanel Poder <a href="http://blog.tanelpoder.com" target="_blank"
>http://blog.tanelpoder.com</a> <div class="Ih2E3d">
 > -- --Original Message-- -- > From: <a href="mailto:oracle-l
-bounce@(protected)">oracle-l-bounce@(protected)</a> > [mailto:<a href
="mailto:oracle-l-bounce@(protected)">oracle-l-bounce@(protected)
</a>] On Behalf Of Luis > Fernando Cerri > Sent: Thursday, November
01, 2007 23:20 > To: <a href="mailto:oracle-l@(protected)">oracle-l
@(protected)</a> > Subject: CPU Time calculation in AWR Reports
 > > Hello, list. > > At Statspack age, 'CPU Time&
#39; 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 <a href="http://e.name" target="_blank">e.name</a>  
         = 'CPU used > by this session'
 >                    
      and
<a href="http://b.name" target="_blank">b.name</a>        
   = 'CPU used > by this session'; > > 
 </div><div><div></div><div class="Wj3C7c">-- <a href="http://www
.freelists.org/webpage/oracle-l" target="_blank">
http://www.freelists.org/webpage/oracle-l</a> </div></div><
/blockquote></div>