This topic explains how to use the z/OS operating system's macros for controlling I/O devices. z/OS DFSMS Macro Instructions for Data Sets explains how to invoke each of these time-saving features. To varying degrees, each macro is device dependent, so you must exercise care if you want to achieve device independence. You can adapt your application to various device types by issuing the DEVTYPE macro. See z/OS DFSMSdfp Advanced Services.
This topic covers the following subtopics.
When you use the queued access method, only unit record equipment can be controlled directly. When using the basic access method, limited device independence can be achieved between magnetic tape and direct access storage devices. With BSAM you must check all read or write operations before issuing a device control macro.