z/OS MVS JCL Reference
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z/OS MVS JCL Reference

Identifies the relative position of a data set on a tape volume. Before z/OS® V1R5 the value of the data-set-sequence-number on the LABEL parameter was limited to 9999. However, starting with z/OS V1R5, the system allows data set sequence numbers up to 65535 for the following media:
  • Standard label (SL) tapes, including standard user label tape (SUL) and leading tape mark (LTM).
  • Unlabled (NL) tapes.
  • Bypass label processing (BLP)
For data set sequence numbers greater than 4 decimal digits, up to 65535, you must use the OPEN macro instruction in your application as follows:
  • For uncataloged data sets, update the data set sequence number in the JFCB and use the OPEN,TYPE=J macro.
  • For catalogued data sets, use the OPEN macro. The catalog provides the data set sequence number.
If you do take advantage of data set sequence numbers above 4 decimal digits, you should modify any non-IBM applications that print tape labels or access the tape labels directly, because the data set sequence number in the SL label might not be in EBCDIC format.. For additional information on data set sequence numbers, see z/OS DFSMS Macro Instructions for Data Sets.
Omit this subparameter or code 0 or 1 to indicate the first data set on the tape volume. Also omit this subparameter for the following:
  • Cataloged data sets. The system obtains the data-set-sequence-number from the catalog.
  • A DD DSNAME parameter that requests all members of a generation data group (GDG). The system retrieves the data-set-sequence-number from the catalog.
  • A data set passed from a preceding step. The system obtains the data-set-sequence-number from the passing step.

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