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RE: CBO question ?

From: Baumgartel, Paul <paul.baumgartel_at_credit-suisse.com>
Date: Thu, 2 Mar 2006 16:50:58 -0000
Message-ID: <D97D1FAE0521BD44820B920EDAB3BBAC0A189F27@ENYC11P32005.corpny.csfb.com>


Venu,  

Consider yourself corrected ;-). An earlier posting on this contained the relevant section of the Oracle documentation, which states clearly that CBO is used if there are statistics on any table in the query. Results will probably be poor unless there are statistics for all tables (and their indexes).  

Paul Baumgartel
paul.baumgartel_at_credit-suisse.com
212.538.1143

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Andem, Venu Sent: Thursday, March 02, 2006 11:41 AM
To: oracle-l_at_freelists.org
Subject: RE: CBO question ?

Paul,  

I think its the other way round, if one of the tables in the query does not contain statistics then Oracle uses RBO. pls correct me if i am wrong.  

Venu

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Baumgartel, Paul Sent: 02 March 2006 15:31
To: oracle-l_at_freelists.org
Subject: RE: CBO question ?

If any table mentioned in the query has statistics stored in the data dictionary, Oracle will use the CBO.  

Paul Baumgartel
paul.baumgartel_at_credit-suisse.com
212.538.1143

-----Original Message-----
From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Savio Pinto (s) Sent: Thursday, March 02, 2006 10:28 AM
To: oracle-l_at_freelists.org
Subject: CBO question ?

Hi,

The execution plan for a query in oracle 9i shows "Optimizer= CHOOSE", how can i force the DB engine to use the COST based optimization for a query ?

Oracle version is 9.2.0.4.0

Thanks
Savio Pinto


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Received on Thu Mar 02 2006 - 10:50:58 CST

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