The DFSMShsm ABARS installation exits must be accessible by the LOAD macro and must communicate with the standard MVS linkage for registers. Registers on Entry to DFSMShsm ABARS Installation Exits and Registers on Return from DFSMShsm ABARS Installation Exits describe standard MVS linkage with which DFSMShsm complies. The exits must save and restore registers. DFSMShsm does not place return codes in the registers; it includes them as parameters in the parameter list for exits that provide return codes. An installation exit cannot issue the DFSMShsm supervisor call instruction (SVC).

Each exit parameter list contains pointers to the information described in the discussion of each individual exit. It points to copies of the information unless specifically stated otherwise.

Because DFSMShsm responds differently to abends that occur for different exits, the actions DFSMShsm takes are described for each exit. Generally, when an exit abends, DFSMShsm issues a HOLD on the function, writes a message, and does not call the exit again until either a DFSMShsm RELEASE command releases the function or a SETSYS command requests the function.

If an exit abends and you require a dump for problem determination, see z/OS DFSMShsm Diagnosis. Exits are not subject to TRAP commands.

Table 1 lists the hex values for exits that do selective processing based on the device type DFSMShsm is processing.