Re: high cpu on query

four things can change an exec plan:

1) change in text of sql
2) change in init params
3) change in object stats (tables and indexes)
4) change in system stats

i'm pretty sure that if those four things don't change then your plan can't change. do you have a job collecting system stats?

-Jeremy

On 6/29/07, Joe Armstrong-Champ <joseph.armstrong-champ_at_tufts.edu> wrote:
>
> We upgraded to 10.2 a month ago and everything was running fine until 2
> days ago when a query started running very slow in prod. It is selecting
> data from a view using distinct and does an 'order by', too. It runs ok
> in a copy of the db which was refreshed just after the upgrade. The
> difference in the number of rows between the 2 databases isn't that much
> but the execution plans are very different. The indexes are the same in
> both. I manually updated the stats for the affected tables in another
> copy which was refreshed yesterday but the plan didn't change. There is
> a high percentage of cpu involved in the long running query.
>
> Questions:
> - what can cause a difference in the execution plans besides the stats
> and indexes?
> - in general what can cause a query to use a lot of cpu?
>
> Thanks.
> Joe
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

-- 
Jeremy Schneider
Chicago, IL
http://www.ardentperf.com/category/technical

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