Re: SIEBEL PERFORMANCE RBO to CBO
- From: "LS Cheng" <exriscer@xxxxxxxxx>
- To: paulastankus@xxxxxxxxx
- Date: Sun, 4 Feb 2007 02:17:46 +0100
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@xxxxxxxxx> 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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