Re: Question on Parallel ORACLE on NCR 3600

Carolyn Binder (cbinder_at_crl.com) wrote:
: Parallel Oracle Scenario (loosely coupled):
: Assume there are two processors on an SMP, sharing an Oracle database.
: If one requests a block of information that the other one has in memory,
: how will the data be obtained? I figured that the requesting process
: would end up getting the info from the memory of the other, rather than
: doing disk i/o, which'd be slower.
 

: The real reason I'm asking this is because I'm trying to understand how
: parallel Oracle works on an NCR 3600 box we're looking at. We want to
: reduce intraprocessor communication between APs because the Ynet is slower
: than an AP's internal bus. The reps are telling me that very little
: communication goes across the Ynet, and *no* database data travels on the
: Ynet. So in the case above, how do the processors exchange data? Far as
: I know, the YNET is what connects the two Aps; I think I'm missing something.
 

: Reply to either me or the newsgroup. Personally, I'd rather see more
: answers posted to the newsgroup, rather than emails to the posters; it
: makes for more interesting stuff to read! Thanks.
 

: Carolyn Binder cbinder_at_crl.com

Hi,

As I have understood the Oracle parallel server, the communication between two ( or more ) takes place via 'distributed lock manager' and this is apparantly true on ALL plateforms. When instance A requests a block which is in instance B's SGA , the knowledge of which is communicated by 'dlm', the block WILL be obtained by A via disk - an act which is called 'ping'. That is why, the distribution of locks/file is VERY important and more important is to know the application. If the user population across two nodes primarily does the 'same' thing, OPS , in all probability, will give inferior performance compared to single instance. Basically the communication between the instances HAS to take place via disk. However, there are some tricks by which the performance can be improved dramatically !!

Pl. feel free to mail in case you need more info !

By the way, have I answered your question ?!!!!!!

Amit

--
                                  _____________
    Amit Gupta                        churchill        Tel: +44 81 313 5688
    Sr. Database Administrator    =============        Fax: +44 81 313 5699
    Churchill Technology Ltd.
    15-17 London Rd, Bromley BR1 1DE, UK.    Email: amit_at_churchill.co.uk