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" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED] 06/08/01 07:40 AM
|
To: Multiple recipients of list ORACLE-L <[EMAIL PROTECTED]> 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
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