The following is a list of device-dependent macros and macro parameters. Consider only the logical layout of your data record without regard for the type of device used. Even if your data is on a direct access volume, treat it as if it were on a magnetic tape. For example, when updating, you must create a new data set rather than attempt to update the existing data set.

OPEN—Specify INPUT, OUTPUT, INOUT, OUTIN, OUTINX, or EXTEND. The parameters RDBACK and UPDAT are device-dependent and can cause an abnormal end if directed to the wrong device type or to a compressed format data set on DASD.

READ—Specify forward reading (SF) only.

WRITE—Specify forward writing (SF) only; use only to create new records or modify existing records.

NOTE/POINT—These macros are valid for both magnetic tape and direct access volumes. To maintain independence of the device type and of the type of data set (sequential, extended-format, PDSE, and so forth), do not test or modify the word returned by NOTE or calculate a word to pass to POINT.

BSP—This macro is valid for magnetic tape or direct access volumes. However, its use would be an attempt to perform device-dependent action.

SETPRT—Valid only for directly allocated printers and for SYSOUT data sets.

CNTRL/PRTOV—These macros are device dependent.

CLOSE—Although CLOSE is a device-independent macro, the system performs processing at task termination that differs between device types. If the task terminates abnormally due to a determinate system ABEND for an output QSAM data set on tape, the close routines that would normally finish processing buffers are bypassed. Any outstanding I/O requests are purged. Thus, your last data records might be lost for a QSAM output data set on tape.

However, if the data set resides on DASD, the close routines perform the buffer flushing which writes the last records to the data set. If you cancel the task, the buffer is lost.