By means of the FILE or FCB macro (LABEL operand) or via the ADD-FILE-LINK command (LABEL-TYPE operand), the user specifies that a tape file is to be created with standard labels, where the value specified is the exchange level in accordance with DIN 66029. figure 7 (Single-volume file: one file on one tape) shows the structure of a tape file with standard labels.
Volume header label (VOL1)
The first block on a tape is the volume header label VOL1; this may be used only after the BOT marker. The VOL1 label contains the volume serial number (VSN), the owner identifier and flags indicating whether or not the tape is shareable and the DIN standard with which the tape and file labels comply.
DIN 66029 permits up to 9 volume header labels, but BS2000 writes only VOL1. When reading tapes from non-BS2000 systems with multiple volume header labels, DMS ignores all such labels except VOL1.
For information on label processing see chapter "Label processing when opening tape files".
End-of-volume labels (EOV)
For files which extend over several tapes, these labels identify the end of a tape (volume) and thus the end of a file section. The last data block of a file section is followed first by a tape mark, then by the end-of-volume labels, and finally by a double tape mark.
DIN 66029 permits up to 9 end-of-volume labels (EOV1, ..., EOV9), but BS2000 supports only a maximum of three (EOV1, EOV2, EOV3); only these three labels are written and the labels EOV4...EOV9 are ignored when a tape is read.
For information on label processing see chapter "EOV processing".
File header labels (HDR)
Each file is preceded by file header labels. These identify the file and contain the file attributes, i.e. their function is similar to that of the entry in the F1 label of a private disk.
DIN permits up to 9 file header labels (HDR1, ..., HDR9), but BS2000 supports only a maximum of three (HDR1, HDR2, HDR3). Only these three labels are written and the labels HDR4...HDR9 are ignored when a tape is read.
The file header labels are always followed by a tape mark. If a file extends over several tapes (multivolume file), each file section begins with file header labels, which follow the volume header label.
For information on label processing see chapter "Label processing when opening tape files".
End-of-file labels (EOF)
The last data block is always followed by a tape mark and then the end-of-file labels which, like the file header labels, identify the file and are used to monitor access to the file.
DIN 66029 permits up to 9 end-of-file labels (EOF1, ..., EOF9), but BS2000 supports only the labels EOF1-EOF3; only these labels are written and the labels EOF4...EOF9 are ignored when a tape is read.
The end-of-file labels are followed by a tape mark if there are more files on the tape. If this is the last file on the tape, the end-of-file labels are followed by a double tape mark.
For information on label processing see chapter "CLOSE processing".