Re: Analysing SYS tables

On Fri, 05 Dec 97 17:23:34 GMT, g.r.s.deisz_at_ptt-telecom.unisource.nl (g.r.s. deisz) wrote:

>Hi all,
>
>Does someone have any experience using the cost-based optimiser to access
>tables owned by SYS?
>Oracle Support advises not to analyse SYS tables in order to make sure the
>rule based optimiser will be used accessing these tables.
>Does this mean that Oracle has not been able to make the cost based optimiser
>good enough to guarantee performance?
>
>Thanks in advance,
>
>Stefan.
>
>
>--
>Name :G.R.S. Deisz
>Phone :+31-50-5855954
>E mail :G.R.S.Deisz_at_PTT-Telecom.Unisource.NL
>DISCLAIMER:This statement is not an official statement from, nor
> does it represent an official position of, PTT Telecom BV.
 

Under verion 7, I found the cost based optimiser to be far from reliable. For most statements, it seemed to produce only small improvements, if any. For some statements, it could be drastically wrong.

I generally stuck to the rule based optimiser, or "hand-optimised" the statements using hints. Version 8 has at least fixed the bug where performing a range search with a bind variable automatically prevented the use of an index on the column involved. Received on Mon Dec 08 1997 - 00:00:00 CST