Re: Question about the ALWAYS_ANTI_JOIN init parameter

The parameter you mention is only taken into account using the cost based optimizer. IMO, still using the Rule Based Optimizer is very undesirable. If you can't change it, for whatever reason, you have a problem, because a well-tuned application using CBO, will, IMO, clearly outperform RBO. Also using RBO, you can not use Parallel Query, function based indexes etc, etc, etc and RBO will be deleted soon, as it has been desupported in Oracle 7.1. Somehow,IMO, in the near future, you should reconsider using RBO.

Regards,

Sybrand Bakker, Oracle DBA

"Tobin M. Johnson" <johnsont_at_wi.rr.com> wrote in message news:3A6518C9.2D8F3C59_at_wi.rr.com...
> I'm looking for specifics about the differences between the three
> possible values for the ALWAYS_ANTI_JOIN parameter. It appears that
> the default is NESTED_LOOPS, and seems to work OK on our system, but
> what about the MERGE and HASH values? I know they will change how
> queries are executed, but how much different will they be?
>
> Specifics about the system I'm talking about:
> - DB engine runs with OPTIMIZER_MODE=RULE (for reasons I'll not get
> into with this post, I cannot change this value).
> - The system is an OLTP system, typically with about 10GB of data
> spread over 280 tables, about 100 of which are large and/or high
> volume.
> - Using Oracle 7.3, Oracle 8 and Oracle 8i on various systems.
> - Most (>90%) queries are using indexes or primary keys to access
> data.
>
> Any insight you folks have will help me out.
>
> Tobin Johnson
> Oracle DBA
> Catalyst International
Received on Tue Jan 16 2001 - 23:22:02 CST