Re: Chache??

Hi Marc,

Do you use the explain option with TKPROF ? If so, what do the execution plans tell you ?

When you say you execute the same cursor, are you using bind variables or are they identical hard coded values ?

When you say the I/O numbers go up, is the cumulatively or individually ?

*How* Oracle determines the execution plan is dependent on which optimizer you use. Cost Based uses statistics on the tables (if they're there) to determine the "cheapest" option and not so much on how you write your statement per se.

For your question to be appropriately answered you need to provide some more details. Version of database, platform, optimizer mode, list of execution plans, table statistics, available indexes etc.

To answer your question 'What does Oracle do ?' requires these details.

But for me it's bedtime, although if you post these details I'm sure some else will be able to assist.

Good Night

Richard

"Marc Zinzen" <mzinzen_at_genese.de> wrote in message news:3D92F6C7.B6DEBE4D_at_genese.de...
> Hi Richard.
>
> Thank you for your exclusive reply. It makes alot of sence and this is
actually
> what i read (except ofcours the alter table flush shared pool). But this
is what
> bothers me. I have ran 4 queries. They are identical over 4 different
Cursors on
> the same table. I then looked at the report TKPROF gives me. The I/O
> access-numbers go UP, not DOWN. I dont know why. Its amazing.
>
> Any ideas?
> What I'm doing this all for: i need to figure out how Oracle works its
> predicates! Centura DB goes from left to right. So the most discriminating
> predicate should be the first. I know Oracle does a lot of optimizing. But
in
> case the optimizer doesn't provide the answer. What does Oracle do???
>
> Marc
>
Received on Thu Sep 26 2002 - 09:00:53 CDT