Re: Fed Up with being a DBA

domenicg_at_hotmail.com (Domenic G.) wrote in news:c7e08a19.0309120603.22b699f7_at_posting.google.com:

> Daniel,
>
> You make some good points, but I'm not paid by the hour! DBCA is OK
> for beginners, but I like to use a script so that I can hit all the
> functionality. As for COST, of course it works great for
> function-based indexes, query rewrite, partitioning, bitmap-join
> indexes, but if I want a straight NL with index scans on the join keys
> with one index scan on the driving table, COST seems to outsmart
> itself more often than not. For skewed columns, it works great. The
> whole concept behind COST is to LEAN AWAY from indexes when you're
> joining entire tables. Still, RULE is useful is certain situations,
> and if Oracle decides to desupport it, I'll kill them. I was able to
> increase system performance on one DB 20 times by simply changing to
> RULE -- COST kept doing hash joins when only a few rows were selected
> and the column was indexed!!!
>
> Domenic.

The only time I find the RBO better is when you want a nested loops join . If CBO isn't giving it you just supply the appropriate hints - ordered and use_nl. Received on Fri Sep 12 2003 - 10:29:40 CDT