IBM® supplies a functional sample USERVAR exit routine under the VTAM® module, ISTEXCUV, in SYS1.SAMPLIB. The sample exit is specific to the Transaction Processing Facility (TPF) environment. This topic contains sections of code from the sample exit routine.

IBM supplies both source code and object code for this routine. You can use the sample USERVAR exit routine as it is coded, modify the sample, or write your own exit routine. You can obtain a complete current listing of the sample exit routine by printing the file. If you write your own USERVAR exit routine, you should use the interface information described in USERVAR exit routine. See USERVAR exit routine for TPF sessions for a discussion of the function of the sample USERVAR exit.

The sample USERVAR exit allows session users to request TPF services by using predefined generic names for the TPF application programs. VTAM calls this exit for exit activation, exit deactivation, when a USERVAR needs to be added, updated, or deleted, or when there is a request to find the best control logical unit (CLU) for a session.

The logon manager defines its USERVARs as volatile. The sample USERVAR exit translates only volatile USERVARs so that the logon manager can ensure proper load balancing and maintain CLU session limits. When the sample exit receives a translation request for a static or dynamic USERVAR, the exit turns off the translation flag, sets a nonzero return code, and returns control to VTAM.