Kernel configuration

 

WebSphere MQ uses semaphores and shared memory. It is possible, therefore, that the default kernel configuration is not adequate.

Before installation, review the machine's configuration and increase the values if necessary. The minimum recommended values of the kernel parameters are given in Figure 1. These values might need to be increased if you obtain any First Failure Support Technology™ (FFST™) records.

  1. If you intend to run a high number of concurrent connections to WebSphere MQ, we recommend that you increase the number of kernel timers, or CALLOUTS as they are known. You configure the number of CALLOUTs available using the NCALLOUT kernel parameter. By default, NCALLOUT is equal to (16 + NPROC), where NPROC is the total number of processes allowed on the system. As WebSphere MQ is threaded, you could choose a value similar to (16 + NKTHREAD). However, there is an overhead in kernel memory for every CALLOUT defined, so tune this value to the requirements of the individual system.

  2. Semaphore and swap usage does not vary significantly with message rate or message persistence.

  3. WebSphere MQ queue managers are generally independent of each other. Therefore system kernel parameters, for example shmmni, semmni, semmns, and semmnu need to allow for the number of queue managers in the system.

See the HP-UX documentation for information about changing these values.

Figure 1. Minimum recommended kernel parameter values 
   shmmax           536870912
   shmseg           1024
   shmmni           1024
   shmem            1
   sema             1
   semaem           16384
   semvmx           32767
   semmns           16384
   semmni           1024 (semmni < semmns)
   semmap           1026 (semmni +2)
   semmnu           16384
   semume           256
   maxusers         32
   max_thread_proc  66
   maxfiles         10000
   maxfiles_lim     10000
   nfile            10000

You must restart the system once you have made any changes to the kernel parameters.

 

System Resource Limits

Set the system resource limit for data segment and stack segment to unlimited using the following commands in a command prompt: 
ulimit -d unlimited
ulimit -s unlimited

 

Parent topic:

Installation procedure


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