Re: What does an app need to do to work with RAC

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_at_hcresources.co.uk> 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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> http://www.freelists.org/webpage/oracle-l
>
>
>

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Anjo Kolk
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