RE: optimizer_index_cost_adj and optimizer_index_caching
- From: "Niall Litchfield" <n-litchfield@xxxxxxxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 05 Mar 2004 15:55:11 +0000
Hi wolfgang
I actually asked dan fink about this at UKOUG, because I haven't seen any
investigations into system stats anywhere, do you have some evidence, links etc
looking into the use of system stats anywhere? It instinctively sounds a good
idea to me, but one that has the capability of blowing up in ones face. I
don;'t like explosions much - I do like trying to do things the right way.
Niall Litchfield
Oracle DBA
Audit Commission
+44 117 975 7805
> -----Original Message-----
> From: breitliw@xxxxxxxxxxxxx
> Sent: 05 March 2004 15:04
> To: breitliw@xxxxxxxxxxxxx; oracle-l@xxxxxxxxxxxxx
> Subject: Re: optimizer_index_cost_adj and optimizer_index_caching
>
>
> If you are using Oracle 9, forget about O_I_C_A and O_I_C
> (i.e. leave them
> at their default) and use dbms_stats.gather_system_stats
>
> My 0.014938 cents (Canadian currency)
>
> At 07:30 AM 3/5/2004, you wrote:
> >Oracle support(without knowing anything about my system) is
> telling me to
> >use the following settings:
> >
> >OPTIMIZER_INDEX_CACHING = 50
> >OPTIMIZER_INDEX_COST_ADJ = 5
> >
> >Tom Kyte's book effective Oracle by Design recommends starting
> >optimizer_index_caching at my cache/hit ratio and adjusting
> as needed.
> >
> >Tim Gorman's paper 'Search for Intelligent Life in the Cost-Based
> >Optimizer' states that OPTIMIZER_INDEX_COST_ADJ should be
> set between 10
> >and 50 for most OLTPs.
> >
> >This is a hybrid system, but I only have the OLTP parts to
> stress test(the
> >other parts are still in early phase development). Does
> anyone have any
> >opinions on this?
>
> Wolfgang Breitling
> Oracle7, 8, 8i, 9i OCP DBA
> Centrex Consulting Corporation
> http://www.centrexcc.com
>
>
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