High shmmax value in Redhat 6.3

Posted by xpapad on Server Fault See other posts from Server Fault or by xpapad
Published on 2013-05-08T17:20:51Z Indexed on 2013/11/12 21:57 UTC
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We are using Redhat 6.3 with 30G RAM to host our Postgres server.

The (default) shmmax value is 68,719,476,736

In some forums I have read that having an shmmax value larger than the RAM causes extensive paging, but in the Redhat forums it warns against changing a kernel parameter that is already configured to a value larger than the minimum requirements for an environment.

In ServerFault I've read that this probably has no impact.

So is there any impact of having shmmax value > RAM in a DB server, or the kernel understands this and handles it appropriately?

Thanks

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