An application program can determine the installed VTAM's support for session-level security when the application program is assembled and again after the application program has issued OPEN ACB.

To determine VTAM's support for session-level verification when the application program is assembled, the application program can reference the variable &ISTGA07, which is created by the ISTGAPPC macroinstruction. For more information, refer to z/OS Communications Server: SNA Programmer's LU 6.2 Reference.

After the application program has started and completed issuing OPEN ACB, the function-list vector of the access-method-support vector can be checked to determine the installed VTAM's level of support for session-level verification. For information about the access-method-support vector list, see Access-method-support vector list.