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Home -> Community -> Mailing Lists -> Oracle-L -> RE: hinting and the rule based optimizer
Another one of this famous myths.
There are a couple of hints that you can use that will not invoke CBO. I am really sorry to write this email and not been able to check them all up (I have not access to my database from this PC).
If I remember it correctly, you can use cursor_sharing, push_subq (this one was probably a bug) and a third one.
I will check this tomorrow if not someone else do it before me.
Cheers / Jocke Treugut
www.treugut-tuning.com
-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of Juriy.Matey_at_bmo.com
Sent: den 1 april 2004 22:36
To: oracle-l_at_freelists.org
Subject: Re: hinting and the rule based optimizer
Ryan,
the ONLY hint you can use with RBO is /*+ rule */
Any other hint will force using CBO.
Juriy Matey
<ryan.gaffuri_at_cox.net>
Sent by: oracle-l-bounce_at_freelists.org
04/01/2004 03:03 PM
Please respond to oracle-l
To: oracle-l_at_freelists.org
cc:
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.
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