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Unlabeled tapes z/OS DFSMS Using Magnetic Tapes SC23-6858-00 |
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To process or create a tape with no labels, specify NL or LTM (for
VSE tapes) in the LABEL parameter of the DD statement. An unlabeled
tape contains only data records and tape marks. The organization of data sets on one or
more volumes is shown in Figure 1. The system
automatically writes the tape marks on output and expects to find
a similar placement of tape marks on input.
An unlabeled tape can be read backward even though there is no tape mark preceding the first data set. In this case, the end-of-data-set condition is signaled by the reflective strip or other indicator at the beginning of the tape. Open/Close/EOV lookahead mounting does not accept any unlabeled volume that is mounted before the system requests it (UCBNRY=0 and UCBVOLI=zeros). A demount message with a blank vol ser is issued. Note: AVR automatically recognizes mounts of labeled volumes. If JCL-specific
requests are used and a volume that is not specified is mounted at
allocation time, the system requests a demount of the incorrect volume
and a mount of the specified volume. Avoid mounting unlabeled tapes
before the system requests them.
Bypassing label processing (BLP) is identical to NL processing except that the check for an existing label is bypassed. For more information about BLP, see Bypassing label processing. Figure 1. Organization for unlabeled tapes
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Copyright IBM Corporation 1990, 2014
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