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Re: Several CPUs and the parallel option

From: Rick Denoire <100.17706_at_germanynet.de>
Date: Tue, 30 Jul 2002 23:50:01 +0200
Message-ID: <83tdku0jfj28ofj4hktnvpd73uuvileku5@4ax.com>


Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote:

>On Sun, 28 Jul 2002 12:09:56 +0200, Rick Denoire
><100.17706_at_germanynet.de> wrote:
>
>>Put simple, I would like a data mining application to take advantage
>>of the four CPUs of our E3500 (Solaris 2.7, Oracle 8.1.7 Enterprise
>>Edition). When it runs, it only uses effectively one CPU (which is
>>being switched of course). I assume that when using the parallel
>>feature of Oracle, it will then be possible to use several CPUs for
>>one and the same job.
>When posting at least try not to make this a riddle game.
>'When I set the parallel option on in init.ora' --> which parameters
>do you set

parallel_server=true

This is wrong, as I now understand. I only have one server, but this server has several CPUs. So what I need is parallel query, does not need to be installed. Just changing the degree of parallelism of the tables should do the work, or using hints.
>Generally speaking parallel query is useless if your data is not being
>striped across <number of CPUs> disks. Having 4 parallel query slaves
>hit the same disk will definitely not help.

Please correct me:
If data is *striped* in a Raid, then this Raid represents one "disk" in the OS. All I/O requests to this device will be serialized and queued. Parallel query won't translate into parallel I/O operations (of course, internally, data is collected from all disks in the Raid when they are read, so this kind of "parallelims" still remains).

If data is *distributed* (different objects or files on different independent disks) then data transfer would take place in parallel.

To me, it is still unclear if several CPUs are going to be used even when data is on a Raid (striped), assuming that the table has an appropriate degree of parallelism.

Thanks
Bye Received on Tue Jul 30 2002 - 16:50:01 CDT

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