RE: Parallel Query Option

Hi Chris,

PQO is great if you have the hardware to support it. For example, say you have a large table in lots of partitions, and each partition is on a separate device. Then, a query can scan the whole table way faster, since the query is broken into parallel pieces, each scanning a small part - one parition - of the table independently of the others.

If, however, you only have a small number of devices - say, 3 - then even if you only parallelize to two pieces, chances are the two pieces will fight each other over disk access, causing a BIGGER bottleneck and slower response then you would have had with a single nonparallel full table scan.

Your mileage may vary, but my experience has been that PQO worked great with LOTS of disks, not as great with medium number of disks, and not well at all with just a few disks, even striped. (Actually, I wonder if striping would make it better or worse; ins't that always the case with striping...?)

Good luck,

Yosi

> -----Original Message-----
> From: CC Harvest [mailto:ccharvest_at_yahoo.com]
> Sent: Friday, April 20, 2001 12:11 PM
> To: Multiple recipients of list ORACLE-L
> Subject: Parallel Query Option
>
>
> I am trying to tune a 30GB database and to configure
> the initSID.ora files to use PQO. From my understand,
> they are some back requirements: multiple CPUs of the
> machine, stripe the tablespace datafiles, etc. If I
> only have 3 disk drive, do I have to stripe the
> datafiles to 3 disks, index files to 3 disks? Anyone
> has the real example of initSID.ora file to share?
>
> Thanks,
>
> Chris Harvest
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Auctions - buy the things you want at great prices
> http://auctions.yahoo.com/
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author: CC Harvest
> INET: ccharvest_at_yahoo.com
>
> Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
> San Diego, California -- Public Internet access / Mailing Lists
> --------------------------------------------------------------------
> To REMOVE yourself from this mailing list, send an E-Mail message
> to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
> the message BODY, include a line containing: UNSUB ORACLE-L
> (or the name of mailing list you want to be removed from). You may
> also send the HELP command for other information (like subscribing).
>

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: 
  INET: Yosi_at_comhill.com

Fat City Network Services    -- (858) 538-5051  FAX: (858) 538-5051
San Diego, California        -- Public Internet access / Mailing Lists
--------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).