VTAM-supported LU 6.2 application programs have APPC=YES coded on their APPL definition statements. (For details on defining an application program to VTAM®, refer to z/OS Communications Server: SNA Resource Definition Reference.) These LU 6.2 application programs can issue the VTAM APPCCMD macroinstruction, which provides LU 6.2 services. They also can support non-LU 6.2 sessions by using the macroinstructions provided with the record API. The set of assembler-language macroinstructions VTAM offers to its application programs is called the application program interface (API). The application program uses the API by issuing the macroinstructions. Once the system programmer defines the application program to VTAM, the application program is authorized to issue these types of macroinstructions.

LU 6.2 support is a specialized enhancement to the interface that VTAM offers to all its application programs.

For a detailed explanation of the VTAM record API, and of concepts pertaining to all VTAM application programs, refer to z/OS Communications Server: SNA Programming.