Processing End-of-Volume

The access methods pass control to the data management end-of-volume (EOV) routine when another volume or concatenated data set is present and any of the following conditions is detected:

Tape mark (input tape volume).
File mark or end of last extent (input direct access volume).
End-of-data indicator (input device other than magnetic tape or direct access volume). An example of this would be the last card read on a card reader.
End of reel or cartridge (output tape volume).
End of last allocated extent (output direct access volume).
Application program issued an FEOV macro.

If the LABEL parameter of the associated DD statement shows standard labels, the EOV routine checks or creates standard trailer labels. If you specify SUL or AUL, the system passes control to the appropriate user label routine if you specify it in your exit list.

If your DD statement specifies multiple volume data sets, the EOV routine automatically switches the volumes. When an EOV e condition exists on an output data set, the system allocates additional space, as indicated in your DD statement. If no more volumes are specified or if more than specified are required, the storage is obtained from any available volume on a device of the same type. If no such volume is available, the system issues an ABEND.

If you perform multiple opens and closes without writing any user data in the area of the end-of-tape reflective marker, then header and trailer labels can be written past the marker. Access methods detect the marker. Because the creation of empty data sets does not involve access methods, the end-of-tape marker is not detected, which can cause the tape to run off the end of the reel.

Exception: The system calls your optional DCB OPEN exit routine instead of your optional EOV exit routine if all of the following are true:

You are reading a concatenation.
You read the end of a data set other than the last or issued an FEOV macro on its last volume.
You turned on the DCB “unlike” attributes bit. See Concatenating Unlike Data Sets.

Recommendation: If EOV processing extends a data set on the same volume or a new volume for DASD output, EXTEND issues an enqueue on SYSVTOC. (SYSVTOC is the enqueue major name for the GRS resource.) If the system issues the EOV request for a data set on a volume where the application already holds the SYSVTOC enqueue, this request abnormally terminates. To prevent this problem from occurring, perform either step:

Allocate an output data set that is large enough not to require a secondary extent on the volume.
Place the output data set on a different volume than the one that holds the SYSVTOC enqueue.