Re: Does optimizer's behaviour change with this ?

On 2 Jul 2004 02:58:10 -0700, spendius_at_muchomail.com (Spendius) wrote:

>Hi,
>Do you think the # of CPUs on a server is a variable with which
>the optimizer may play ? We've migrated a DB from 8.1.7.1 on
>a 4-CPU machine to 64-bit 8.1.7.4 on an 8-CPU box, and for
>exactly the same activity on this database we're experiencing
>A LOT more CPU usage: do you think the optimizer may iterate
>more to find the best path of a statement since it's found it's
>got more CPUs at its disposal, and thus require more processing ??
>I'm talking about SunOS 5.8 here.
>
>Thanks !
>Spendius

You might be using the Parallel Query option, inadvertently. Using Parallel Query, your requests are being addressed by various Parallel Query slaves, with one coordinator process acting as a broken. This behavior could be easily seen from your execution paths.

My experiments on Parallel Query showed Parallel Query is useless if you have only 4 CPUs, and we decided to switch it off completely.

--
Sybrand Bakker, Senior Oracle DBA