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OMVS segment requirements for TCP/IP communication

MainView TCP/IP communication makes use of z/OS UNIX System Services.

A z/OS UNIX security context, called an OMVS segment, is required for any user ID that requests these services.

To use TCP/IP for CAS-to-CAS communication, each of the following types of users must have access to z/OS UNIX System Services:

  • started tasks (such as a CAS or PAS)

  • TSO user IDs that will be accessing a CAS or PAS (such as the UAS)

  • MainView batch report jobs

You can either define a specific OMVS segment for each user ID or use the default OMVS segment that is provided for users and groups. For more information about defining OMVS segments, see the IBM UNIX System Services Planning.

When you are defining OMVS segments for MainView TCP/IP users, be aware of the following requirements:

  • OMVS segments must be defined before you update any CAS definitions to activate TCP/IP communication.

  • The PROCUSERMAX value for a PAS must be high enough to support the maximum number of concurrent users in the PAS.


If you do not specify PROCUSERMAX in the OMVS segment for a PAS, the number of processes is limited by the OMVS system parameter MAXPROCUSER. If you assign the same UID to multiple PASs (or share a UID by default), the MAXPROCUSER value applies to the total number of processes in all address spaces that share the same UID.

  • The MAXPROCSYS value must be high enough to support the increased number of OMVS processes that results from using MainView TCP/IP communication.

The default value specified for MAXPROCSYS in BPXPRMXX is 900. MainView requires 1 process for each connection plus approximately 10 processes for each PAS to support the permanent tasks that run in each address space.

To display the current MAXPROCSYS value and the high-water mark for OMVS processes, issue the following system command:


To change the MAXPROCSYS (or MAXPROCUSER) value, use the SETOMVS system command.

After you have defined the necessary OMVS segments and updated the CAS definition with TCP/IP information, you must stop and restart the CAS for the changes to take effect.

When a CAS or PAS that is using TCP/IP communication initializes, a message like the following is displayed:


In this case, an OMVS segment was defined for the assigned user name, MVSSTC.

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