Program interruption control area

The expansion of each standard or list form of the SPIE macro contains a system parameter list called the program interruption control area (PICA). The PICA contains the new program mask for the interruption types that can be disabled in the PSW, the address of the exit routine to be given control when one of the specified interruptions occurs, and a code for interruption types (exceptions) specified in the SPIE macro. For the mapping provided by the IHAPICA mapping macro, see PICA in z/OS MVS Data Areas in the z/OS Internet library.

The system maintains a pointer (in the PIE) to the PICA referred to by the last SPIE macro executed. This PICA might have been created by the last SPIE or might have been created previously and referred to by the last SPIE. Before returning control to the calling program or passing control to another program through an XCTL or XCTLX macro, each program that issues a SPIE macro must cause the system to adjust the SPIE environment to the condition that existed previously or to eliminate the SPIE environment if one did not exist on entry to the program. When you issue the standard or execute form of the SPIE macro to establish a new SPIE environment, the system returns the address of the previous PICA in register 1. If no SPIE/ESPIE environment existed when the program was entered, the system returns zeroes in register 1.

You can cancel the effect of the last SPIE macro by issuing a SPIE macro with no parameters. This action does not reestablish the effect of the previous SPIE; it does create a new PICA that contains zeroes, thus indicating that you do not want an exit routine to process interruptions. You can reestablish any previous SPIE environment, regardless of the number or type of subsequent SPIE macros issued, by using the execute form of the SPIE specifying the PICA address that the system returned in register 1. The PICA whose address you specify must still be valid (not overlaid). If you specify zeroes as the PICA address, the SPIE environment is eliminated.

Figure 1 shows how to restore a previous PICA. The first SPIE macro designates an exit routine called FIXUP that is to be given control if fixed-point overflow occurs. The address returned in register 1 is stored in the fullword called HOLD. At the end of the program, the execute form of the SPIE macro is used to restore the previous PICA.

Figure 1. Using the SPIE Macro

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        SPIE   FIXUP,(8)   Provide exit routine for fixed-point overflow
        ST     1,HOLD      Save address returned in register 1
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        L      5,HOLD      Reload returned address
        SPIE   MF=(E,(5))  Use execute form and old PICA address
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HOLD    DC     F'0'