Parallel queries in RAC environment

From: James Barton <>
Date: Wed, 15 Oct 2008 14:03:43 +0100
Message-ID: <>

4-node RAC,

I have a long-running batch process. I suspect that some of the queries it contains would run faster with multiple read processes, and I'm trying to test this out.

I've hinted the relevant queries with

/*+ parallel (table_alias 6) */

and I can see that six read processed do start. The problem is that they are all on another instance than the original batch process. This results in a lot of block swapping and I actually see a slight degradation in performance. Currently I'm starting the batch process as a scheduled job, and the job class it belongs to has a service that is available on only one instance. Still, the child processes are on another instance - they don't seem to inherit the service from the parent process.

How can I force all of the child query processes to be on the same instance as the parent process?


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Received on Wed Oct 15 2008 - 08:03:43 CDT

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