Using dynamic versions of the Open/Close/End of Volume Tape exits

Previous to z/OS V2R2, any changes to Open/Close/End of Volume tape installation exit routines required an IPL before taking effect. Starting in V2R2, z/OS provides dynamic versions of these tape installation exits: Volume Mount, File Start, File Validate, File End, and Label Anomaly. You can modify the dynamic versions of these exits and implement them without an IPL. Appropriate sections of the ‘IFGTEP OCE Tape exit parameter list’ macro are used to map the dynamic exits’ parameter lists. Each dynamic exit receives the same parameter list as the corresponding non-dynamic exit. The dynamic tape installation exits are as follows:

OCE_VOLUMEMOUNT
OCE_FILESTART
OCE_FILEVALIDATE
OCE_FILEEND
OCE_LABELANOMALY.

The z/OS system defines the dynamic exits as AMODE 31, reentrant, and persistent until the next IPL. If an ABEND occurs in one of the exit routines associated with a dynamic exit, that exit routine becomes inactive while others stay active.

By default, each dynamic tape installation exit is associated with one IBM-supplied dummy exit routine:

IFG019VM – Volume mount dummy exit routine
IFG019FS – File start dummy exit routine
IFG019FV – File validation dummy exit routine
IFG055FE – File end dummy exit routine
IFG019LA – Label anomaly dummy exit routine.

After the system is IPLed you can see the dynamic Open/Close/End of Volume exits by issuing an MVS DISPLAY command such as the following: D PROG,EXIT,EX=OCE_*

You can also see an exit’s diagnostic data with an MVS DISPLAY command, such as the following example for the volume mount exit: D PROG,EXIT,EX=OCE_VOLUMEMOUNT,DIAG

You can keep or delete the IBM-supplied dummy exit routines, and can add your own exit routines, using MVS system commands as described in section "Using Dynamic Exits" of z/OS MVS System Commands. You can also use a PROGxx member of SYS1.PARMLIB. If an exit routine for a tape dynamic exit is defined in PROGxx, then it will be added to the exit during IPL and will be visible using a DISPLAY command thereafter. If no exit routines are defined in PROGxx, then the IBM-supplied dummy exit routine will be added to the exit.

You can associate multiple exit routines with one dynamic installation exit. Each defined exit routine must be a separate load module in AMODE 31 and reentrant. Changes to the exit routines become available without IPL. If multiple exit routines are defined for one installation exit, they are called one at a time.

Note: the mapping macro for each exit defines which fields are read-write, and the other fields must not be changed.

Exit-specific details for the dynamic exits, including return code handling for multiple exit routines, are given in the sections for each exit in this chapter.