End-of-Volume on output
The system's EOV routine automatically switches volumes when one of the following EOV conditions occur:
- The reflective strip on a reel is encountered
- The logical end of a tape cartridge is reached
- The FEOV macro is executed
This volume switching includes:
- Checking whether the expected number of blocks were read or written (see Verifying block count)
- Writing trailer labels and a tape mark on the current volume
- Ensuring that the next volume is mounted
- Checking existing volume and header labels on the new volume
- Writing a volume label on the new volume
- Writing header labels and a tape mark on the new volume
When multiple tape units are used, the EOV routine also checks
to see if a next-plus-one volume is needed, and if the volume just
written can be rewound and unloaded. If so, the EOV routine issues
a message directing the operator to mount the next-plus-one volume
on the tape unit just used. This is a premounting aid; the next-plus-one
volume label is not verified at this time. This lookahead or parallel
mounting results in an IEC501E mount
message.
Note: The IEC501E message has a type 2 descriptor code that causes
the message to be retained on the screen.
If you do not want message
retention, turn off the message retention attribute. You can accomplish
this by either:
- Specifying RETAIN(NO) for the message id in an MPFLSTxx record
- Using a WTO message exit (an MPF specific exit or IEAVMXIT) to alter the message descriptor code or to request "do not retain this message"
For tape mounts, the IEC501E message remains on the screen until the mount is satisfied or until EOV has occurred on the previous volume. EOV deletes the IEC501E message and issues the IEC501A message.