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Data Set Labels -- Magnetic Tape<br />
The blocks of information that serve as<br />
labels for data sets residing on magnetic<br />
tape are the data set label 1 and the data<br />
set label 2. For IBM standard tapes these<br />
blocks are 80 bytes long and are in EBCDIC<br />
characters in main storage and on<br />
nine-track tape, and in BCD characters on<br />
seven-track tape.<br />
A set of a data set label 1 and a data<br />
set label 2, together with user labels (if<br />
used), is used to make up header labels,<br />
end-of-volume trailer labels, and<br />
end-of-data-set trailer labels. separate<br />
diagrams and descriptions are presented for<br />
these different formats:<br />
• Da ta Set Label 1 (FL1).<br />
• Data Set Label 2 (FL2).<br />
Tapes recorded in ASCII have different<br />
label requirements. These tapes, when<br />
created by the IBM <strong>System</strong>/360 Operating<br />
<strong>System</strong>, follow the conventions of the<br />
American National standards Institute.<br />
Significant differences between IBM<br />
standard labels and American National<br />
Standard labels are as follows:<br />
• Data set label 2 (FL2) is optional<br />
under American National Standards.<br />
• Because of word-length requirements of<br />
some computer manufacturers, labels<br />
longer than 80 characters may be<br />
present on ASCII tapes.<br />
• The American National Standards do not<br />
support seven-track tape; all of their<br />
standard labels are recorded in ASCII<br />
on nine-track tape.<br />
Data Set Labels -- Magnetic Tape 193
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