Re: Clusters and CBO

Sorry 8.1.7EE

Various platforms mainly NT

"Jonathan Bliss" <bliss_jonathan_at_nossspam.hotmail.com> wrote in message news:vcS19.2148$sH3.63606_at_newsfep1-win.server.ntli.net...
> Hi
>
> I am working with an application originally written in Oracle 6. A major
> set of reference tables are built as a cluster. These reference tables
are
> highly normalized and self referencing. i.e. an item in the main table
can
> be related to other items in the same table that can be in turn related to
> others. The application appears to run more slowly with the CBO than with
> the rule based optimizer thus the live environment uses the RBO. The
> culprit appears to be when multiple aliases of the reference tables are
> used. The entire application is written in PL\SQL. I didn't write it.
>
> 1. Should the CBO *always* outperform the RBO.
> 2. Are clusters one instance this may not be the case.
> 3. Is Oracle really going to take away the RBO
>
> Tests suggest that rebuilding the tables without the cluster, computing
> stats and using CBO may not degrade performance but it takes courage to
bite
> the bullet with the live system.
>
> Any thoughts appreciated.
>
> Jonathan
>
>
Received on Wed Jul 31 2002 - 09:17:41 CDT