Re: Bitmap index costing - how to influence

From: Wolfgang Breitling <>
Date: Sun, 29 Mar 2009 15:01:42 -0600
Message-Id: <>

The opt_param hint is documented, albeit only in the Oracle 11i SQL Reference Manual even though it is also available in 10g (R2 at least, haven't tried it in 10.1.x ):

"The OPT_PARAM hint lets you set an initialization parameter for the duration of the current query only. This hint is valid only for the following parameters: OPTIMIZER_DYNAMIC_SAMPLING, OPTIMIZER_INDEX_CACHING, OPTIMIZER_INDEX_COST_ADJ, OPTIMIZER_SECURE_VIEW_MERGING, and STAR_TRANSFORMATION_ENABLED."

At 06:02 AM 3/29/2009, Randolf Geist wrote:
> > Why use undocumented OPT_PARAM when INDEX_COMBINE is documented and
> > provided?
>thanks for making that point. I generally second that one shouldn't
>use undocumented parameters/features if possible. Unfortunately
>Oracle doesn't provide (yet) an officially documented way to
>influence parameters like OICA / OIC on statement level, that's why
>I suggested it in this particular case to limit the effects of this
>parameter as much as possible.
>There are obviously many different possibilities how the index usage
>in this particular case could be hinted/forced, but the
>INDEX_COMBINE and the OPTIMIZER_INDEX_COST_ADJ suggestions provide
>quite different means, so it depends what the objective is in the
>particular situation.


Wolfgang Breitling
Centrex Consulting Corporation

Received on Sun Mar 29 2009 - 16:01:42 CDT

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