Under certain circumstances, empty file sections may occur at the start or end of a tape in an MF/MV set, e.g. if end-of-tape is detected while the labels are being written. DMS then initiates a tape swap and finishes writing the labels on the next tape.
Empty file section at the start of a tape
If the system detects the end of the tape when it is writing the last data block of a file or the end-of-file labels, it terminates the tape with end-of-volume labels and a double tape mark. After the next tape has been mounted, the system writes the volume header label, followed by the file header labels of the file which was not completed, a double tape mark and, finally, the end-of-file labels.
If this file is the last file of a file set, a double tape mark is then written to terminate the set. If further files follow in the set, only a single tape mark is written, followed by the HDR labels of the next file.
Empty file section at the end of a tape
If the system detects the end-of-tape mark while writing the file header labels for a file, it writes the end-of-volume labels, enclosed between two double tape marks, immediately after these file header labels.
The next tape starts with the volume and file header labels, the file section number in the HDR1 label being incremented by 1. This is followed by a tape mark and then the first section of the file.
