Operating System configuration and tuning for IBM MQ on AIX® systems

File descriptors

When running a multi-threaded process such as the agent process, you might reach the soft limit for file descriptors. This limit gives you the IBM® MQ reason code MQRC_UNEXPECTED_ERROR (2195) and, if there are enough file descriptors, an IBM MQ FFST file.

To avoid this problem, increase the process limit for the number of file descriptors. You must alter the nofiles attribute in /etc/security/limits to 10,000 for the mqm user ID, or in the default stanza. To alter the number of file descriptors do these steps:

In a command prompt, check the maximum number of file descriptors available to a process running as mqm:
```
lsuser -a nofiles mqm
```

Set the value to at least 10240:


chuser nofiles=10240 mqm
chuser nofiles_hard=10240 mqm

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

Attention: For an mqm user ID other than root, the value unlimited might not be permitted.

For more information on configuring your system, see How to configure UNIX and Linux® systems for IBM MQ.

You can check your system configuration using the mqconfig command.

Swap space

During high load IBM MQ can use virtual memory (swap space). If virtual memory becomes full it could cause IBM MQ processes to fail or become unstable, affecting the system.

To prevent this situation your IBM MQ administrator should ensure that the system has been allocated enough virtual memory as specified in the operating system guidelines.