Re: parallel query performance

From: <Riyaj_Shamsudeen_at_i2.com>
Date: Fri, 08 Jun 2001 06:45:03 -0700
Message-ID: <F001.003221B5.20010608064026@fatcity.com>

Hi Elain
        Yes, that is true. SGA is useful if you want to cache the block, so that many sessions can avoid the disk reads. But, in case of Parallel Query architecture, mostly, only the parallel query slave is interested in the block. That's why slave process directly reads the blocks in to the PGA bypassing the Buffer cache. Of course, object level checkpoint occurs and there are some optimization in 8i versions.  That is the reason, there is no point in increasing the buffer cache, if most of the work is done through parallel query slaves.

But, the communication buffers between the slave processes are stored in the shared pool though.

Thanks
Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA
i2 technologies   www.i2.com

"elain he" <elainhe_at_hotmail.com>
Sent by: root_at_fatcity.com
06/08/01 07:40 AM
Please respond to ORACLE-L

       
        To:        Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
        cc:        
        Subject:        parallel query performance

Hi,
Is it true that when running parallel query, the parallel query slaves do not read from buffer cache even though the data resides in the buffer cache ie the slaves read directly from disk.

Does not make sense to me. Can someone clarify that?

Thanks.

elain

---

Get your FREE download of MSN Explorer at http://explorer.msn.com

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: elain he
  INET: elainhe_at_hotmail.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).

Received on Fri Jun 08 2001 - 08:45:03 CDT