Your SYNAD routine can end by branching to another routine in your program, such as a routine that closes the data set. It can also end by returning control to the control program. The control program then returns control to the next sequential instruction (after the macro) in your program, after a basic access method or if the queued access method is honoring EROPT=AC or EROPT=SKP. If your routine returns control, the conventions for saving and restoring the contents of registers are as follows:

• The SYNAD routine must preserve the contents of registers 13 and 14. The routine must also preserve the contents of registers 2 through 12 if the logic of your program requires their preservation. On return to your program, the contents of registers 2 through 12 will be the same as on return to the control program from the SYNAD routine.
• Register 13 contains the address of a save area that the control program uses. The SYNAD routine must not use this save area. If the routine saves and restores register contents, it must provide its own save area.
• If the SYNAD routine calls another routine or issues supervisor or data management macros, it must provide its own save area or issue a SYNADAF macro. The SYNADAF macro provides a save area for its own use, and makes this area available to the SYNAD routine. A SYNADRLS macro must remove such a save area from the save area chain before control is returned to the control program.