RE: Recipe for application design to run on RAC

Hmm. Oracle says that with the improved Cache Fusion in 9i, any current application can be taken "as is" and run on 9iRAC. But yes, you are right. It really depends on the speed at which the two instances can share the same block and this can never be the same as two sessions accessing the same block in one instance [one SGA].
We are currently running and 8.1.5 OPS [ouch !] environment and testing 9iR2 RAC. The 8.1.5 OPS runs such that the Application Servers [Pro*C servers which get transactions from remote devices through a "message bus"] all connect to one node and direct PCs using VB/MSQuery connect to the other. Time and again I've asked for the PCs also to connect to the same node but no ... the effort to update the TNSNAMES.ORA and ODBC setup on the PCs would be too much I am told. In 9iRAC we are testing both BASIC and PRECONNECT Failover for TAF and will most certainly be using both nodes of the cluster for transactions. Even the Application Servers will be connecting across both nodes.
Cross-fingers, touch-wood and wish me luck !

Hemant

At 03:59 PM 26-11-02 -0800, you wrote:
>If two or more RAC instances will be trying to cache the same data
>blocks, then this causes the performance problems that you'll see show
>up as lots of time spent on the event called "global cache cr request".
>If you can partition your application so that RAC nodes don't have to
>share blocks very often through the cache fusion mechanism, then your
>system will scale a lot better.
>
>
>Cary Millsap
>Hotsos Enterprises, Ltd.
>http://www.hotsos.com
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>
>-----Original Message-----
>Sent: Tuesday, November 26, 2002 3:34 PM
>To: Multiple recipients of list ORACLE-L
>
>Dear List,
>
>Number of times I've seen that one of prerequsites for
>switching from single node DB to OPS/RAC is to have an
>application specifically designed / architectured to
>run on RAC.
>Can somebody elaborate? Is it something "visible" on
>ERD? That is by looking at the model can RAC guru tell
>that it wouldn't work well on RAC?
>Or put it another way can one conclude based on the
>ERD that app was modeled to run on RAC?
>
>What's the recepie for app design for RAC?
>
>TIA
>
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Hemant K Chitale
My web site page is : http://hkchital.tripod.com

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