Purging and Restoring I/O Requests (PURGE and RESTORE macros)

The system's purge routines perform either a halt or a quiesce operation. In a halt operation, the purge routines stop the processing of specified I/O requests initiated with an EXCP or EXCPVR macro instruction. In a quiesce operation, the purge routines includes the following procedures:

Allow the completion of I/O requests (initiated with an EXCP or EXCPVR macro instruction) that were passed to the system for execution and are executing
Stop the processing of requests that have not yet been initiated or passed to the system, but save the IOBs of the requests so they can be reprocessed (restored) later.

The system's restore routines make it possible to reprocess I/O requests that are quiesced.

Restriction: Purge and restore processing performed for I/O requests that are not initiated by an EXCP or EXCPVR macro is not covered here. User applications that use the PURGE and RESTORE macros with the sequential access method (SAM) against partitioned data sets (PDSs) (for example, to synchronize the I/O) cannot do so against PDSEs, sequential extended format data sets, or z/OS® UNIX files, because SAM does not use EXCP or EXCPVR to access these types of data.

To pass control to the purge and restore routines, build a parameter list and place its address in register 1, then issue the macro instruction.

24-bit or 31-bit addressing mode can be used for the PURGE or RESTORE macro (and the parameter list).