Re: Optimal degree of parallelism

You have Parallel_automatic_tuning=true ... so why are you using the hint ?

What happens if 3 of you log in and run that statement ?

I think then 27 processes can be started to service those 3 users

no. of users x ((2*DOP)+QC process)) (since each worker slave might start a producer-consumer )

3x((2*4)+1)=27

ref

http://download-west.oracle.com/docs/cd/A87860_01/doc/server.817/a76965/c22p aral.htm#3166

HTH
"Saikat Chakraborty" <saikatchak_at_hotmail.com> wrote in message news:afdba21d3ba630845c624b85a812673c.16981_at_mygate.mailgate.org...
> Hi,
> Situation
> IBM AIX 4.3.3
> CPU count 4
> Oracle 8.1.7.4 Enterprise Edition.
> We are setting parallel query in statement level as
>
> select /*+ parallel(emp,4) */ from emp;
>
> Tables are large enough to utilize parallel query.
>
> One of my fellow DBA is telling me:
> <QUOTE>
> As the general rule, the optimal degree of parallelism can be safely set
> to n-1 where n is the number of processors. That means 3 not 4.
> </QUOTE>
>
> I serached google, oracle documents and metalink for this "general rule"
> but never found any reference to it.
> Usually I set number of parallel slaves in powers of 2 and never set
> this to a odd value.
> Is it a myth or I am missing something ?
>
> Thanks,
> Saikat Chakraborty
>
>
> --
> Posted via Mailgate.ORG Server - http://www.Mailgate.ORG
Received on Mon Sep 01 2003 - 07:00:01 CDT