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Did you know that you can limit access to system functions by registering which users can access which functions? You can allow access or deny access via the function usage capabilities; depending on the component, you could allow one user to change some settings and allow another user to only view those settings. Many system components support the use of function usage capabilities to provide more granular access to their capabilities. Functional usage does not eliminate or replace the need for securing resources on your system; it simply provides an additional way to control what functions a user can access.

There are:

The User Function Registration Facility API set was first introduced into the system way back in V4R3, so this capability has existed for quite a while. The commands were introduced in V5R3, which improved ease of use since a program no longer had to be written to implement it.

The first use of limiting function access within the operating system was in the V4R5 release when the Trace Connection (TRCCNN) command was introduced. Service commands required *SERVICE special authority; but *SERVICE special authority is quite powerful, and it’s very likely that you’ll want to allow someone to collect a dump or a trace, but not want them to have *SERVICE special authority. Today, most all of the service commands (trace, dump, watch) are supported with customized access via functional usage.

Since the introduction of TRCCNN, more system components have added support for granular access via functional usage. You can see the full list of functions supported with the DSPFCNUSG or WRKFCNUSG commands by taking the default of *ALL. The GUI also provides a list of all functions that are available.

The GUI for this capability can be found under SystemApplication Administration as well as SecurityApplication Administration; it is the Host Applications category that provides this support.

  • Default Access allows all users to access the function by default
  • All Object Access allows all users with all object system privilege to access the function
  • Customize allows you to add or remove users or groups in the Access Allowed and Access Denied lists.

The following screen capture shows the kind of information you can see with the Display Function Usage command. In my example, you can see that I have allowed user DAWNMAY to access trace functions, even though DAWNMAY may not have *SERVICE special authority. User DAWN is not allowed to access trace functions.

08202012 DawnMay3

This blog post was edited for currency on February 21, 2020.

This blog post was originally published on IBMSystemsMag.com and is reproduced here by permission of IBM Systems Media.