RE: hinting and the rule based optimizer

From: Justin Cave (DDBC) <jcave_at_ddbcinc.com>
Date: Thu, 1 Apr 2004 13:32:22 -0700
Message-ID: <87E9F113CEF1D211A4C30090273018741BBA50@ddbcinc.ddbc.local>

One simple rule-- don't hint (other than /*+ RULE */). By design, any = hinted statements will invoke the CBO, as will any number of database = features (i.e. partitioning).

Justin Cave
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC

-----Original Message-----

From: oracle-l-bounce_at_freelists.org =
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of ryan.gaffuri_at_cox.net Sent: Thursday, April 01, 2004 1:04 PM
To: oracle-l_at_freelists.org
Subject: hinting and the rule based optimizer

We have a legacy 8.1.7.3 instance that is in RBO mode. My group does not = own it, so we cannot change it to CBO.

When I hint anything from an index to ordered, etc... it switches to the = CBO and since nothing is analyzed, it's an even worse plan... Not = allowed to analyze the tables either because it's not our property.

Any rules around hinting the RBO in 8.1.7.3? Why would it switch to the = CBO from a simple hint? I never use the RBO so please bare with me.=20

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Received on Thu Apr 01 2004 - 14:42:34 CST