IBM standard label processing
- Checking the labels on input tapes to ensure that the correct volume is mounted, and to identify, describe, and protect the data set being processed
- Checking the existing labels on output tapes to ensure that the correct volume is mounted, and to prevent overwriting of vital data
- Creating and writing new labels on output tapes
- For volumes in an automated tape library, comparing the external volume serial number to the magnetically recorded internal label
These processing functions are summarized in Table 1. The table shows the specific labels that are processed for each function and which routines perform the functions.
Processing | Volume Label VOL1 | Header Labels1 | Trailer Labels1 | ||||
---|---|---|---|---|---|---|---|
HDR1 | HDR2 | UHL1-8 | EOF1 or EOV1 | EOF2 or EOV2 | UTL1-8 | ||
First or only volume2 | |||||||
Checks labels on input tape | Open | Open | Open | Open | EOV | Bypassed | EOV |
Checks existing labels on output tape before overwriting | Open | Open | Open | Not read | Not read | Not read | Open3 |
Writes new labels on output tape | Open or user4 | Open | Open | Open | Close or EOV | Close or EOV | Close or EOV |
Compares the volume serial number on the external volume label to the serial number in the tape volume label6 | Open | Open | N/A7 | N/A7 | N/A7 | N/A7 | N/A7 |
Second or subsequent volumes5 | |||||||
Checks labels on input tape. | EOV | EOV | Bypassed | EOV | EOV | Bypassed | EOV |
Checks existing labels on output tape before overwriting. | EOV | EOV | Not read | Not read | Not read | Not read | Not read |
Writes new labels on output tape. | EOV or user4 | EOV | EOV | EOV | Close or EOV | Close or EOV | Close or EOV |
Compares the volume serial number on the external volume label to the serial number in the tape volume label6 | EOV | N/A7 | N/A7 | N/A7 | N/A7 | N/A7 | N/A7 |
Notes:
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When a data set is opened for input, the volume label and HDR1 are processed. HDR2 is processed if it exists. For an input end-of-data condition, the trailer labels are processed, unless deferred user input trailer label processing is specified in the DCB exit list. For an input end-of-volume condition, the trailer labels on the current volume are processed, and then the volume label and header labels on the next volume are processed. When the FEOV macro is issued for an input tape, the trailer labels on the current volume are not processed, but the volume labels and header labels on the next volume are processed. No label processing is performed when an input data set is closed, unless deferred user input trailer label processing is specified in the DCB. If deferred user input trailer label processing is specified, the processing otherwise performed for an input end-of-data condition is performed when an input data set is closed.
When a data set is opened for output, the existing volume label and HDR1 label are checked, and a new volume label and new header labels are written. For an output end-of-volume condition (including FEOV), trailer labels are written on the current volume, the existing volume and header labels on the next volume are checked, and then a new volume label and new header labels are written on the next volume. When an output data set is closed, trailer labels are written.