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Home -> Community -> Mailing Lists -> Oracle-L -> Re: optimizer_index_cost_adj and optimizer_index_caching
Oh, the search for Good Numbers. Will probably never stop. But should.
Tim Gorman wrote:
> Ryan,
>
> My paper recommended setting O_I_C_A to a value calculated from observations
> from V$SYSTEM_EVENT for the wait-events "db file sequential read" and "db
> file scattered read". It does mention values like "10" and "50" in the very
> beginning of the paper, just to set expectations, but then recommends using
> observed values as it forward references the entire remainder of the paper.
>
> The quote you mention came from the "Cut to the Chase" section in the very
> beginning, which was intended as an "executive summary" for those (PHB,
> CIOs, CTOs, VPs of IT, etc) who would not care to read all the way through.
> It was immediately followed by a section (comprising the remaining 95% of
> the text) entitled "The Rest of the Story"...
>
> Hope this helps...
>
> -Tim
>
> P.S. Ironically, I do recommend a fixed value for O_I_C of 90, because I
> have never felt that it was worth the brain cycles to attempt to find a good
> observed value of the BCHR. Just set the thing to 90, accept the "discount"
> it provides on the cost calculation, and move on...
>
>
> on 3/5/04 7:30 AM, ryan.gaffuri_at_cox.net at ryan.gaffuri_at_cox.net 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? >> >> >>---------------------------------------------------------------- >>Please see the official ORACLE-L FAQ: http://www.orafaq.com >>---------------------------------------------------------------- >>To unsubscribe send email to: oracle-l-request_at_freelists.org >>put 'unsubscribe' in the subject line. >>-- >>Archives are at http://www.freelists.org/archives/oracle-l/ >>FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html >>-----------------------------------------------------------------
-- Archives are at http://www.freelists.org/archives/oracle-l/ FAQ is at http://www.freelists.org/help/fom-serve/cache/1.html -----------------------------------------------------------------Received on Sun Mar 07 2004 - 18:52:56 CST
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