I found the following question in my blog statistics:
“can we change kernel parameter in linux when oracle is running”
The answer is: Yes, of course!
You can alter any kernel parameter as long as it don’t require a reboot. If you set any kernel parameter to a lower value than your running database requires there wont be any impact in time – but there might be problems when your database continues to run (e.g. unable to start new sessions, degraded performance).Once your database is shut down and you lowered for instance the SHMMAX parameter you wont be able to start the instance.
Therefore you should make sure to increase the values and check twice!