EOV 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 (in the case of a density conflict or version conflict)
Writing header labels on the new volume

If a density or a version conflict occurs when the volume label is checked, a new label (Version 3 or Version 4) is written in the density or the version specified by the user. If any VOL2 - VOL9 or user volume labels (UVLs) exist, they are overwritten. If the original volume label is longer than 80 characters, the excess characters are truncated when the new volume label is written.

When multiple tape units are used, the EOV routine 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.