You enable LU 6.2 support for an application program by specifying the APPC=YES operand on the APPL definition statement. The application program must use the APPCCMD macroinstruction to send and receive data on LU 6.2 sessions and must allow VTAM® to manage LU 6.2 session establishment and termination. This means that an application program cannot use non-LU 6.2 VTAM macroinstructions such as OPNDST, SEND, or RECEIVE on LU 6.2 sessions; however, the same application program can use non-LU 6.2 macroinstructions to communicate on non-LU 6.2 sessions. For information about macroinstructions for LU 6.2 sessions, see the z/OS Communications Server: SNA Programmer's LU 6.2 Guide.

Existing application programs that have implemented LU 6.2 without VTAM APPCCMD support (and consequently use the restricted non-LU 6.2 macroinstructions) should not have APPC=YES on their APPL definition statement. They do not work if it is included. To take advantage of VTAM support, they must be migrated to use the APPCCMD macroinstruction.