Re: Init. param. OPTIMIZER_PERCENT_PARALLEL > 0 ?

From: Rick Denoire <100.17706_at_germanynet.de>
Date: Mon, 10 Nov 2003 22:38:58 +0100
Message-ID: <ptuvqvkcmud9ujb9lvkaur1kppa1eoeagv@4ax.com>

"Jonathan Lewis" <jonathan_at_jlcomp.demon.co.uk> wrote:

>    a)  when opt_pct_para is zero, Oracle 'assumes'


>        that it will be taking a serial path at run time,

>        and optimises for that (which means that if it

>        executes that path in parallel it may be very

>        bad news for your machine).


Oracle optimizes for serial path and could still execute in parallel?

Does that mean that one should try to conciliate what Oracle optimizes

for with the actual execution plan? So if a table has an option of parallel degree 4, then the session dealing with this table should have a high opt_percent_parallel? (Assuming parallelity is switch on in the init.ora).

According to this statement, if one leaves opt_percent_parallel at zero (default), then every time Oracle executes something in parallel, it will follow a plan which was optimized for serial execution, (i.e. will always be "wrong" or inappropriate). Astonishing.

I think I understood your explanation. I am missing the sense of such logic.

Bye
Rick Denoire Received on Mon Nov 10 2003 - 15:38:58 CST