The use of parmlibs allows you to tailor operations to your own installation requirements, which improves the performance of XRC. Most of the XRC control values that parmlib can alter are centralized in a tuning table.
With parmlib support, you can modify the values of the XRC tuning table by using the XSET command or parmlib parameters. In general, you should not change these values. The default values set for certain XRC parameters work for most customer configurations. However, through experience or testing, some users have found that they can help improve XRC performance by increasing or decreasing the default values.
With parmlib support, you can set up your environment before starting XRC. This makes it easier to track changes and offers more control over your system. Afterwards, you can dynamically override some parmlib parameters by issuing the XSET command. The corresponding XSET parameters are included in parentheses next to the associated parmlib parameter.
Recommendation: Exercise caution when changing the default values associated with the tuning table. It is recommended that you contact an IBM® representative before you attempt any change to the tuning table values.