Kernel configuration

WebSphere® MQ makes use of System V IPC resources, in particular shared memory and semaphores. The default configuration of these resources, supplied with your installation, is probably adequate for WebSphere MQ but if you have a large number of queues or connected applications, you might need to increase this configuration.

You can determine the amount of System V IPC resources available by looking at the contents of the following files:
  /proc/sys/kernel/shmmax - The maximum size of a shared memory segment.
  /proc/sys/kernel/shmmni - The maximum number of shared memory segments.
  /proc/sys/kernel/shmall - The maximum amount of shared memory
                              that can be allocated.
  /proc/sys/kernel/sem    - The maximum number and size of semaphore sets
                              that can be allocated.
For example, to view the maximum size of a shared memory segment that can be created enter:
  cat /proc/sys/kernel/shmmax
To change the maximum size of a shared memory segment to 256 MB enter:
  echo 268435456 > /proc/sys/kernel/shmmax
Start of changeTo view the maximum number of semaphores and semaphore sets which can be created enter:
cat /proc/sys/kernel/sem
This returns 4 numbers indicating:Start of change
 SEMMSL - The maximum number of semaphores in a sempahore set
 SEMMNS - The maximum number of sempahores in the system
 SEMOPM - The maximum number of operations in a single smeop call
 SEMMNI - The maximum number of sempahore sets  
End of change Start of changeFor WebSphere MQEnd of change: Start of changeEnd of change Start of changeTo increase the maximum number of semaphores available to WebSphere MQ, you should update the SEMMNS and SEMMNI values.End of changeEnd of change

To configure these values every time the machine is restarted you are recommended to add these commands to a startup script in /etc/rc.d/...