Daniel Roy wrote:
>>What happens if you throw in a hint like FIRST_ROWS? Would the
>>optimizer accept the hint ?
>
>
> If you throw any hint to a query (except "RULE"), cost-based
> optimizing is triggered. In that case, since you probably don't have
> any stats for your tables, Oracle will try to make up these stats by
> itself, using criteria such as number of extents used by a table (to
> estimate its size), ... Oracle usually does a decent job at making up
> these stats (from what I've seen), but of course it would be much
> better to have real up-to-date stats if you intend to use CBO for some
> queries. If you decide to go that route (use hints and gather the
> stats), make sure that OPTIMIZER_MODE (for the instance running
> Siebel) is RULE (and not CHOOSE), or otherwise CBO will be used for
> all the queries (including the ones from the Siebel application)
> running against the database, and your Siebel TAM will slap your
> fingers.
>
> Daniel Roy
> IBM
> Siebel/Oracle Consultant
Thanks for the headsup, Roy. I think you've given me a couple of
questions that I need to discuss with the DBA.
Received on Mon Apr 05 2004 - 17:09:59 CDT
