Re: Migrating to cost based optimizer

hasta_l3_at_hotmail.com wrote:
> Dear group,
>
> Our applications are supporting Oracle 8.1.7 and Oracle 9, for many
> customers with varying level of activity.
> We use the rule based optimizer to ensure the stability of the sql
> statement's execution plans.
>
> We are thinking of moving to the cost based optimizer, at least in
> Oracle 10.
>
> Would you have a strategy to recommand ?

Test, test, and test. Don't just throw CBO into production without testing as thoroughly as possible.

> What is the first Oracle release with a cost based optimizer working
> reasonably well ?

While others mention 8.1.7.4, my inlicination is that I wouldn't use CBO until 9.2.0. The CBO was must more stable in that version and makes better decisions. And it gets better in 10g.

> How do you check the performances of your applications across oracle
> releases and customers with that optimizer ?

How do you check the performances of your applications with any optimizer or any version? The fact that you are using CBO does not change this, neither does the Oracle version. The application has to perform well enough to meet any defined SLA performance metrics and eliminate user pain.

HTH,
Brian

-- 
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Brian Peasland
dba_at_nospam.peasland.net
http://www.peasland.net

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Now pick two out of the three" - Unknown