One option would be to:
- collect outlines for the app whilst running under
rule
- change to cost but use the outlines
- piecemeal remove each outline and see if the sql
runs the same (or better). If yes, then this sql is
now "cbo-enabled", if not, look at changing sql
hth
connor
- Sam Bootsma <SamB_at_cpas.com> wrote: > Hello All,
>
> At our site, we are use rule based optimization. We
> are careful to write
> SQL that performs well under this mode. Some of our
> SQL also contains
> hints. When we provide our application to clients,
> we default it to use
> Rule-based. However, some clients may choose to run
> our application in
> cost-based mode. This will be as simple as
> analyzing all tables and indexes
> in our schemas', and changing the mode to use cost
> based.
>
> My Questions:
> 1. How likely is it that our application will
> perform worse under
> cost-based than it does under rule-based. What has
> been the experience of
> others on the list who have moved from Rule-based to
> Cost-based?
> 2. What are some of the underlying reasons for
> performance to decline when
> making such a move? What are some "gotchas" to
> watch for?
> 3. Is there more that needs to be done to move from
> rule to cost? (Other
> than changing the optimization mode and analyzing
> tables and indexes)?
>
> Most clients run our database on NT, although some
> use UNIX. Assume Oracle
> 9i. Our database (at client sites) tends to be
> small, with the largest
> being about 25 GB.
>
> Thanks for any suggestions,
>
> Sam Bootsma
> Technical Support Analyst
>
> --
> Please see the official ORACLE-L FAQ:
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> --
> Author: Sam Bootsma
> INET: SamB_at_cpas.com
>
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Received on Fri Apr 05 2002 - 15:36:14 CST
