Re: Parallel query option

Hi Ed,

first what database version do you work with? Do you have multiple processors? If you don't you probably won't benefit from parallel query
Is the data spread on different disks? If it isn't the disk spindle can't read two places on disk at the same time so you won't benefit here either.

There are some views ( V$PQ_SYSSTAT , V$PQ_SESSTAT, V$PQ_SLAVE) where you can notice activity.
Check V$OPTION if parallel query is true.

Make sure you are doing full table-scans because else the cost based optimizer would probably not choose to do a parallel query. This doesnt mean you must force full table-scans but if it isn't doning a full table scan it won't use PQO.

Greetings,

John

Ed Stevens <Ed.Stevens_at_nmm.nissan-usa.com> schreef in berichtnieuws 8f9pic$rhm$1_at_nnrp1.deja.com...
> One of our database is used for a data warehouse and the queries tend
> to be big, complex multi-table joins - 10 tables is not uncommon.
> Suspecting that parallel query option might help performance, I am just
> starting to look at that, so this may be the question of someone
> looking to buy a clue . ..
>
> I ran an Oracle Expert (from the OEM Tuning Pack) analysis on the DB.
> In recommended reducing parallel_min_servers to zero. The justification
> was "This instance is currently configured to utilize parallel query,
> and is creating query servers at instance startup. THE DEGREE OF
> PARALLELISM IN THE DICTIONARY IS NOT CONFIGURED TO ALLOW PARALLEL QUERY
> PROCESSING. (emphasis mine) At the same time, there is no evidence that
> hints are being provided through the SQL statements."
>
> OK, so I queried dba_tables to see what the values of DEGREE, and
> INSTANCES was for the application tables. I was surprised to see that
> several (though by no means all) of the tables had DEGREE values of
> greater than one, while some had vaules of 'default."
>
> So I guess I have a couple of questions. First, what do I look at to
> see if we are actually getting parallel processing, and to what degree?
> Second, if we're NOT getting it, what more do I need to do to enable
> it?
>
>
> --
> Ed Stevens
> (Opinions are not necessarily those of my employer)
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Tue May 09 2000 - 00:00:00 CDT