An LU 6.2 application program must issue an OPEN macroinstruction, which points to an ACB, to formally present itself to VTAM®. LU 6.2 application programs must also be defined to VTAM using APPC=YES on the APPL definition statement. The OPEN ACB also plays a role in the recovery of a persistent LU-LU session.

LU 6.2 applications can inform VTAM about application capabilities during OPEN ACB by building an application-ACB vector list. The address of the application-ACB vector list is indicated on the PARMS=APPLVCTR parameter of the ACB macroinstruction. For more information about the application-ACB vector list, see Vector lists used during OPEN processing.

Refer to z/OS Communications Server: SNA Programming for detailed information about opening an ACB.