Entry procedures

In general, when an exit routine is entered, the following apply:
  • Register 1 contains the address of a parameter list. ( Table 2 summarizes the parameter list for the EXLST exit routines.) This parameter list is freed when the exit routine returns control to VTAM®.
  • Register 14 contains an address for returning control after the exit routine completes. Unless stated otherwise in the discussions of the specific exit routines, VTAM returns control to the instruction in the application program that is about to be executed when the exit routine interruption occurs.

    If the exit routine is running under an SRB, different conditions apply for return. See Execution of exit routines.

  • VTAM's registers do not have to be saved; register 13 does not contain the address of a VTAM save area. However, when a LERAD or SYNAD exit routine is entered, register 13 does contain the address of an 18-word save area supplied by the application program.
  • VTAM does not provide a save area for the application program's general registers. If any executable VTAM macroinstruction is issued in the exit routine, the address of the exit routine's own 18-word save area must be in register 13 when the macroinstruction is issued.
Parent topic: Procedures to follow in writing exit routines