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?