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Re: SIEBEL PERFORMANCE RBO to CBO

From: LS Cheng <exriscer_at_gmail.com>
Date: Sun, 4 Feb 2007 02:17:46 +0100
Message-ID: <6e9345580702031717s1f9f7b48if84bc551869d2163@mail.gmail.com>


Hi

Have you followed Siebel recommendatio on CBO?

The recommendation they make makes CBO runs like RBO, for example set OPTIMIZER_MAX_PERMUTATIONS to 100 and OPTIMIZER_INDEX_COST_ADJ to 1. 30 tables joins is quite normal in Siebel, over 45 is not unusual.

AFIAK when you switch to CBO (from Siebel 7.7) by default internally Siebel runs these SQL statements to optimize client queries

ALTER SESSION SET OPTIMIZER_MODE = FIRST_ROWS_10 ALTER SESSION SET HASH_JOIN_ENABLED = FALSE ALTER SESSION SET _OPTIMIZER_SORTMERGE_JOIN_ENABLED = FALSE ALTER SESSION SET _OPTIMIZER_JOIN_SEL_SANITY_CHECK = TRUE You should try to trace a client session and see what it is doing.

On 2/3/07, Paula Stankus <paulastankus_at_yahoo.com> wrote:
>
> We have made a number of changes to optimizer parameters and generated
> statistics in our Siebel database migrated to 10g from 8i (i.e. rule-based
> to cost-based optimizer). However, we still see significant response time
> differences between the two versions. I am thinking of using outlines to
> make Siebel on 10g behave and have the same execution plans as Siebel on
> 8i.
>
> Has anyone else had experience in doing this?
>
> Thanks in advance,
> Paula
>
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Received on Sat Feb 03 2007 - 19:17:46 CST

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