RE: Index clustering factor

From: Stephens, Chris <>
Date: Wed, 9 Jan 2008 14:37:08 -0600
Message-ID: <>

I'd first try hinting the index and see if that results in less db work.  

[] On Behalf Of Orysia Husak Sent: Tuesday, January 08, 2008 6:45 PM
Subject: Index clustering factor  

On our database, we have a very simple query that is not using the index that we expected and is instead doing a full tablescan. The clustering factor of this index is very high. Have any of you encountered a similar problem? How have you solved it?  

Have any of you used the technique described in the book Cost-Based Oracle Fundamentals by Jonathan Lewis to adjust the clustering factor of an index using the sys_op_countchg() function?  

Our query is :  

Select * from tableA where fielda=:A and fieldb=:B  

We have an index on tableA (fielda, fieldb), but Oracle isn't using the index.  

The clustering factor of the index is : 1089825  

The table is located in an ASSM type tablespace and the table stats:


  • ----------

   1976721 31517    

I'd appreciate your suggestions ...... or experiences using the sys_op_countchg() function.  

Thank you,


Orysia Husak

Sr. Oracle DBA - Classroom Applications Hosting

University of Phoenix/ Apollo Group, Inc.

Office: 602-557-6934

Mobile: 602-377-8586  

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Received on Wed Jan 09 2008 - 14:37:08 CST

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