The logon manager defines its USERVARs as volatile. The sample USERVAR exit routine processes only volatile USERVARs so that the logon manager can ensure proper load balancing and maintain CLU session limits. When the sample exit receives a request to translate a static or dynamic USERVAR, the USERVAR exit turns off the translation flag and returns a nonzero return code to indicate that the session establishment request failed.

When the sample exit receives a request to translate a volatile USERVAR, the exit processes the request. The exit must first check the OLU status because translation processing when the OLU is the SLU differs from when the OLU is the PLU.

If the OLU is the SLU for the session, the sample USERVAR exit does not translate the name. The exit instead sets the value of the USERVAR equal to the generic USERVAR name. Although the name is not translated, the exit turns on the translation flag. The translation flag must be turned on to ensure that VTAM® drives the logon manager through the logon exit.

If the OLU is the PLU for the session, the sample USERVAR exit processes the translation. All USERVAR translations occur in the logon manager host. The exit queries the logon manager data base by issuing the REQTAIL macro for function code X'04' processing. When called with function code X'04', the REQTAIL macro transfers control to the logon manager. The logon manager invokes the CLU search exit routine to compare all contending CLUs. After the CLU search exit has compared all contending CLUs, it identifies the best CLU for the session. The CLU search exit returns the name of the best CLU to the logon manager. The logon manager finds the application program LU name associated with the best CLU and returns that name to the REQTAIL macro. The REQTAIL macro returns the application program LU name to the USERVAR exit. The REQTAIL macro also returns a completion code indicating the search was successful.