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:[EMAIL PROTECTED]]
> 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
>
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