Re: Performance problem .... HELP :-(

> "Biddell, Ian" wrote:
>
> Hi all,
> Hoping someone can shed some light on a problem I have.
> We a particular cursor in a batch program running in production at a
> client site which has suddenly decided to work really badly.
>
> The program hasn't been changed but I think the customer has done some
> sort of reorg on the database.
> I traced the program on their server and also on a copy of the
> database on our server (our copy taken before the reorg)
> As can be seen from the tkprof output from a trace on the program for
> about an hour theirs does a lot of buffer IO for few rows returned
> compared to ours.
>
> The execution path in the explain is the same but the row counts down
> the side are different.
>
> Does anyone have any idea why this would be happening or what further
> investigation I can do.
> All access is via PK so it should be flying like the second example.
>
> Thanks, Ian
>

Ian,

   It's wrong to believe that because you are using PKs everything should fly. What blinks before my eyes is this :

 179385326 INDEX GOAL: ANALYZED (RANGE SCAN) OF 'RATE_SCHEDULE_LINK_PK' (UNIQUE)    Oracle chooses to access a PK, but as an alternative to scanning what looks like a table implementing a (n-n) relationship of death.

   In other words, it is taking the query by the wrong end. Check what you want (the select list), what you feed in (criteria), and try to coax Oracle in doing it logically, starting from the table for which the best, in terms of selectivity, criterion has been provided. In this kind of case, the /*+ ORDERED */ hint often proves helpful.

-- 
HTH,

Stephane Faroult
Oriole Ltd
-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Stephane Faroult
  INET: sfaroult_at_oriole.com

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