RE: optimizer_index_cost_adj and optimizer_index_caching

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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