Re: Cost versus Rule based Optimizer

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 - 23:21:15 CEST