Re: What does an app need to do to work with RAC
- From: "Anjo Kolk" <anjo.kolk@xxxxxxxxxxx>
- To: john.hallas@xxxxxxxxxxxxxxxxx
- Date: Mon, 29 Jan 2007 11:05:01 +0100
John,
The simple answer to this is: CONTENTION in the application in any form.
What I mean with that is data block contention (the obvious one) but also
ROW CACHE and LIBRARY cache contention. The problem is that synchronizing
between instances will become more expensive if you need to do more of
it.E.g having two nodes going after the same block will cost less than
having 10 nodes going after the same block. The problem is not the number of
nodes, but the contention for the block. So how can one predict what will
happen you go to RAC from a single instance? There are a couple of simple
things one can do to find out (v$latch, v$sysstat, x$kcbsw, etc.), but that
is too much work for this email.
Anjo.
On 1/29/07, John Hallas <john.hallas@xxxxxxxxxxxxxxxxx> wrote:
I will show my ignorance here and ask for what reasons an application
might not work with RAC when more than one instance is added.
Oracle should be able to handle any locks, although there may be timing
delays.
TAF will be dependant upon the application but if the application rolls
sends an 'transaction failed message, please try again' that should be
acceptable shouldn't it.
I know these are very basic questions but as I say it is something I
have wondered about for a while
John
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Anjo Kolk
Owner and Founder OraPerf Projects
tel: +31-577-712000
mob: +31-6-55340888
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