Re: gather stats slows performance?

From: Hans Forbrich <forbrich_at_yahoo.net>
Date: Sat, 07 Aug 2004 21:45:53 GMT
Message-ID: <l4cRc.45138$hw6.14363@edtnps84>

Therre are ever-increasing reasons for CBO, including some features that ONLY work using CBO. From Chapter 1 of Oracle's

Oracle9i Database Performance Tuning Guide and Reference Release 2 (9.2)
Part Number A96533-02

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Features that Require the CBO

The following features require use of the CBO:

• Partitioned tables and indexes
• Index-organized tables
• Reverse key indexes
• Function-based indexes
• SAMPLE clauses in a SELECT statement
• Parallel query and parallel DML
• Star transformations and star joins
• Extensible optimizer
• Query rewrite with materialized views
• Enterprise Manager progress meter
• Hash joins
• Bitmap indexes and bitmap join indexes
• Index skip scans

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Personal suggestion would be to look at the specific queries that are running slower, possibly with the SQL Tuning Advisor of the OEM Diagnostics Pack.

I assume you have a test bed, so taking them one at a time should not be too much of an issue, right? <g>

/Hans Received on Sat Aug 07 2004 - 16:45:53 CDT