Re: SQL Tuning

Samuel wrote:
>
> Hi! Can anyone give me some advices for tuning sql?
>
> I am using the explain plan to fine tune my designed sqls. The optimizer
> mode of my database is in CHOOSE base.
>
> The first it showed me that the cost value of the explain plan is null. It
> means that it used RBO. Then I try to give a all rows hint to this sql and
> re-create the explain plan. Now it showed me the cost value is 2490.
>
> How can I determine which one provide better performance?
>
> Many thanks
>
> Samuel

HI

I presume you've got timed_statistics = true in you init.ora? also you'll need to look at the actual elapsed time. I've seen cases where the 'cost' may be less using an index, but it results in a cartesian join which killed the response time the query went from 10mins to 4 hours!.

martin Received on Thu Feb 17 2000 - 00:00:00 CST