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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Important: Oracle processes taking lots of CPU
Tony,
Yes if Oracle is not waiting but working no wait will be registered. But it should atleast be reflected in "CPU used by this session" stat. It doesn't.
I traced a few processes, but the trace files show no SQL which takes lots of CPU. Moreover, the CPU utlization in the trace file, or in v$sesstat don't match with the actual CPU taken by the process as seen from the OS commands like "top"
Thats why I believe its some kind of O/S issue.
So I did a truss on the process. And I saw the following line repeating infinitely.
select(2048, 0x800003fffdffb3d0, 0x800003fffdffb4d0, 0x800003fffdffb5d0, 0x800003fffdffb6d0) = 0
I'm not sure how to interpret the output of truss, so I posted it in this forum since there are many experts out here, who might be able to interpret it!
Is there any further information I can gather at the O/S level which throws some light on the problem?
As far as statspack is concerned, we haven't implemented statspack, but I did run utlbstat/utlestat and uploaded the output to oraperf.com. It didn't suggested or detect excess CPU/LIOs, since those stats are pretty acceptable in the trace files.
Regards
New DBA
> I'm no expert here, but here *may be* a few things
> to think about:
>
> When Oracle is actually doing something it isn't
> recorded as a wait event,
> e.g. getting a datablock that is in cache doesn't
> generate a wait event.
> If your query is "horrible" you could be using loads
> of CPU without
> generating many waitevents.
>
> A little more dodgy info: "db file sequential
> read" is normally
> accociated with datafile access by rowid, ie. after
> an index lookup.
>
> I think I'd try to find out which queries are
> running during the
> performance problem times and explaining the
> queries.
>
> Also, have you run spreport for this time period?
>
> Told you I wasn't an expert, but I hope that prompts
> other readers to fill
> in the gaps and give you better hints,
>
> Good luck
> Tony
-- http://www.freelists.org/webpage/oracle-lReceived on Tue Nov 23 2004 - 07:29:42 CST
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