Re: Really strange performance issue
- From: Sayan Malakshinov <xt.and.r@xxxxxxxxx>
- To: dombrooks@xxxxxxxxxxx
- Date: Fri, 31 Oct 2014 00:18:23 +0400
This feature usually causes problems if you have at least two cardinality
calculation errors:
1. First cardinality error - the error that causes second plan generating.
2. Second error - cardinality errors for other rowsources in second plan,
because cardinality for them were not saved by this feature in previous
execution. So you we have problem when optimizer work with saved real
cardinality for one rowsource and inconsistent cardinality for others.
This problem can often be resolved by changes statistics gathering
preferences.
On Thu, Oct 30, 2014 at 11:00 PM, Dominic Brooks <dombrooks@xxxxxxxxxxx>
wrote:
> Seen this feature cause a number of degradations. Know quite a few systems
> where they turn it off (and a number of other such features) in the name of
> stability.
>
> Sent from my iPhone--
> //www.freelists.org/webpage/oracle-l
>
>
>
--
Best regards,
Sayan Malakshinov
Senior performance tuning engineer
PSBank
http://orasql.org
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