Controlling the Exit Routine Through the Dynamic Exits Facilities

IBM® has defined the CNZ_MSIEXIT exit to the dynamic exits facility. You can refer to the exit by the name CNZ_MSIEXIT. You can use the EXIT statement of the PROGxx parmlib member, the SETPROG EXIT operator command, or the CSVDYNEX macro to control this exit and its exit routines.

By default, the system disables the exit routine after one abend.

Exit Routine Environment

The exit receives control during Master Scheduler Initialization before the IEFSSNxx parmlib member is processed.

Exit Routine Processing

The exit routine is defined via the PROGxx parmlib member. Dynamic allocation is not available at this point in the IPL, so the exit routine must be defined in LPA, LNKLST or the NUCLEUS. The DSNAME parameter of the EXIT ADD statement in PROGxx should not be used for this exit routine. If it is used, the exit routine does not get control. For example, the PROGxx statement can be EXIT ADD EXITNAME(CNZ_MSIEXIT) MODNAME(MYMSIEXT).

Programming Considerations

You may code your CNZ_MSIEXIT to be reentrant or non-reentrant because the exit is invoked only once for the IPL.

Performance Considerations

While your CNZ_MSIEXIT has control, the IPL of the system does not continue. Therefore, keep the exit processing to a minimum.

Entry Specifications

No parameters will be passed by the exit point to the exit routine, while the 1-8 character parameter PARAM will be passed into the exit routine through Access Registers AR0 and AR1. The value of PARAM parameter is specified in the EXIT statement of the PROGxx parmlib member and in the SETPROG EXIT command.

Registers at Entry: The contents of the registers on entry to the exit are as follows.

Register

Contents

0-12

Not applicable

13

Address of a 72 byte save area

14

Return address

15

Entry point address of the exit

Parameter Descriptions: Register 13 contains the address of a 72 byte save area on entry to the exit routine.

Access Registers AR0 and AR1 contain the data for the 1-8 character parameter PARAM, the value of which is specified in the EXIT statement of the PROGxx parmlib member and in the SETPROG EXIT command. AR0 contains the first 4 bytes, and AR1 contains the second 4 bytes. To get the full 8 bytes of PARAM data, the contents of AR0 and AR1 need to be concatenated.

Return Specifications

Registers at Exit: Upon return from the exit processing, the register contents must be as follows.

Register

Contents

0-15

Restored to contents at entry