Re: why rule based optimizer performs better than cost based?
- From: "Gudmundur Josepsson" <gbj@xxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 25 Jun 2004 23:33:02 -0000
Dick,
Does Dan recommend these values for every OLTP and DSS environments or are
these good values to start working from? Do you know if he's published
anything on this subject that's downloadable from somewhere?
Thanks,
Gudmundur
> Mei,
>
> Take a serious look at two init parameters:
>
> Optimizer_index_caching
> Optimizer_index_cost_adj
>
> The default values are 0 and 100 respectively which inform the optimizer =
> that a) you will never find an index in the buffer cache and b) scanning =
> an index is just as expensive as a table. If any of you are familiar =
> with Dan Hotka, he recently presented his "Index Advance Tuning" seminar =
> at the NOUG DBA SIG here in Boston. His recommendation is to set these =
> to 90 and 30(OLTP) or 50(DSS) respectively. I've tried it, it helps and =
> does not appear to have any unpleasant side effects.
>
> Dick Goulet
> Senior Oracle DBA
> Oracle Certified 8i DBA
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