Configuring and tuning the operating system on AIX

When installing IBM® MQ on AIX® systems, there are some additional settings that must be configured.

About this task

When you install IBM MQ on AIX systems, you must configure the following operating system settings:

File descriptors
System resource limits

Procedure

Increase the process limit for the number of 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, complete the following steps:
1. Check the maximum number of file descriptors available to a process running as mqm:
```
lsuser -a nofiles mqm
```
2. Set the value to at least 10240:
```
chuser nofiles=10240 mqm
chuser nofiles_hard=10240 mqm
```
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.

What to do next

You can check your system configuration using the mqconfig command.

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.

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