You can specify the method of processing (INPUT, OUTPUT, EXTEND, RDBACK, INOUT, OUTIN, or OUTINX) by using an operand of the OPEN macro. If you do not specify the method, INPUT is assumed.

A data set can be processed as either input or output (INPUT, OUTPUT, or EXTEND). A data set on magnetic tape can also be read backward (RDBACK). If the basic sequential access method (BSAM) is used, a data set can also be processed as a combination of input and output (INOUT or OUTIN, or OUTINX). For INOUT, the data set is an input data set first and then, without reopening, an output data set. For OUTIN or OUTINX, the data set is an output data set first and then, without reopening, an input data set. INOUT is not supported for ISO and ANSI tapes except when allowed by the installation label validation exit.