Re: Cost versus Rule based Optimizer

From: <michael_bialik_at_my-deja.com>
Date: Thu, 23 Sep 1999 21:21:15 GMT
Message-ID: <7se5ju$ql3$1@nnrp1.deja.com>

Hi.

You are NOT supposed to analyze SYS and SYSTEM tables. All documentation specifies that CBO may be used only for application schemas.

Michael.

In article <7sal68$8ad$1_at_news1.xs4all.nl>, "Michiel Ploeger" <nospam.Michiel.Ploeger_at_Bluewater-Group.Com> wrote:
> Once I analyzed all tables of my database and had a huge drop in
> performance.
> I deleted the analyzed information of schema SYS and my performance
was
> better then ever.
>
> Is the app developed for cost based or rule based ? Are there any
hints in
> the SQL?
>
> Michiel
>
> Aamer wrote in message <37E89431.5BA7DBBB_at_hotmail.com>...
> >Hi All
> >
> >On checking the database it was found that the tables and schemas
where
> >not analysed. So in fact it was using rule based optimisation. We
> >immediately analysed all schemas .
> > After analysing The buffer hit ratio which was 95% dropped to
84%
> >and the sort in disk increased from 0.5% to 15%.
> >
> >Once we deleted the analysing information it improved the buffer hit
> >ratio to 94% and sort on disk to 6% .
> >
> > Its not understood why when we analysed the buffer hit ration
> >dropped.
> >
> > Aamer_janjua_at_hotmail.com
> >
> > Thanks
>
>

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Share what you know. Learn what you don't. Received on Thu Sep 23 1999 - 16:21:15 CDT