Re: Optimal degree of parallelism

I think I should also post my relevent init.ora parameters

NAME	                                    VALUE
parallel_server	                  FALSE
parallel_server_instances	1
parallel_broadcast_enabled	TRUE
parallel_adaptive_multi_user	TRUE
parallel_threads_per_cpu	2
parallel_automatic_tuning	TRUE
parallel_min_percent	0
parallel_min_servers	2
parallel_max_servers	40
parallel_instance_group	
parallel_execution_message_size	4096

"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

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