Re: Analayze

From: Mahmoud Reza Zare <mrezair_at_0racledba.com>
Date: Wed, 4 Oct 2000 23:02:36 -0700 (PDT)
Message-Id: <10639.118556@fatcity.com>

Dear Hamid,

I think the decision of what kind of optimization to use is global across an instance and is in general COST BASED. You may change this by setting OPTIMIZER_MODE = RULE in your instance's parameter file or force a different optimization using a RULE hint in your SQL statement. As for the effect of that analyze command the optimizer uses the results of the command as stored in the data dictionary and chooses the best navigation plan according to the optimiztion mode. In your case it will use the ANALYZE results on T1 to choose the best navigation where it uses T1 alone or in conjunction with T2 or T3; however for T2 or T3 alone it uses its default assumptions that may not conform to reality.

Good luck
Mahmoud Reza Zare
--- Hamid Alavi <HamidA_at_aimdirect.co.nz>
> wrote:
>Hi,
>
>I have still some few problems affected from ANALYZE result and don't know
>if we have 3 tables EX: T1,T2,T3 and run ANALYZE on just T1 then if SQL
>statment using these 3 tables which optimizer is going to be used?? CBO or
>RBO or both!!!!!!
>
>
>Hamid Alavi
>DDI 3610148
>FAX 3610102
>111 Franklin RD Freemans Bay Auckland
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