When processing a data set, you can test for completion of a READ or WRITE request by issuing a CHECK macro. The system tests for errors and exceptional conditions in the data event control block (DECB). Successive CHECK macros issued for the same data set must be issued in the same order as the associated READ and WRITE macros.

The check routine passes control to the appropriate exit routines specified in the DCB or DCBE for error analysis (SYNAD) or, for sequential or PDSs, end-of-data (EODAD). It also automatically starts the end-of-volume procedures (volume switching or extending output data sets).

If you specify OPTCD=Q in the DCB, CHECK causes input data to be converted from ASCII to EBCDIC or, if CCSIDs are specified for ISO/ANSI V4 tapes, from the CCSID of the data records on tape to the CCSID specified for the application program.

If the system calls your SYNAD or EODAD routine, then all other I/O requests for that DCB have been terminated, although they have not necessarily been posted. There is no need to test them for completion or issue CHECK for them.