Tape marks

The tape mark requirements for ISO/ANSI interchange tapes are:

Each header label group must be followed by a tape mark that indicates the beginning of the data to be processed.
Each data set must be followed by a tape mark that indicates the beginning of the trailer label group.
If the data set is the last one on the volume, each trailer label group must be followed by two tape marks. Otherwise, one tape mark is required.

When creating a data set with Version 3 or Version 4 labels, the system routines write the necessary tape marks.