It is possible to control an I/O device directly while processing a data set with almost any data organization without using a specific access method. The EXCP (execute channel program), EXCPVR, and XDAP macros use the system function that provides for scheduling and queuing I/O requests, efficient use of channels and devices, data protection, interruption procedures, error recognition, and retry. See z/OS DFSMSdfp Advanced Services for information about the EXCP, EXCPVR, and XDAP macros.

Guideline: Do not use the EXCP and XDAP macros to access data. These macros cannot be used to process PDSEs, extended-format data sets, VSAM data sets, UNIX files, dummy data sets, TSO/E terminals, spooled data sets, or OAM objects. The use of EXCP, EXCPVR, and XDAP require detailed knowledge of channel programs, error recovery, and physical data format. Use BSAM, QSAM, BPAM, or VSAM instead of the EXCP and XDAP macros to access data.