Tape labels are a baroque, even roccoco subject, about which I have had to learn more than I wanted to know over the years.
The best [and only current] source for information about them is not the JCL manual; it is the publication z/OS DSFMS using magnetic tapes, newly numbered SC23-6858-00 for z/OS 2.1. Jonathan Postel's notion of robustness can---like any 'principle'---be misused to defend the indefensible. It is perhaps most useful as a heuristic. Highly plausible but in the end fallible conjectures like gmail.com ==> http://gmail.com succeeds most of the time, and attempted disambiguations need not always succeed to be useful. In the words of William James, which I seem to remember using here before, "If a frog jumps at a hook baited with piece of red flannel, too bad for that particular frog; but redness does often signal the presence of edibles, and for the race of frogs . . ." Postel's notion is particularly useful when inputs and outputs can be distinguished sharply. I once wrote a roman- to arabic-numeral and arabic- to roman-numeral conversion routine for a group of art historians. It accepts non-canonical but unambiguous (and surprisingly common in the art-historical literature] roman-numeral inputs like MIM, which it converts into 1999. On the other hand, given 1999 for conversion into a roman numeral, it produces the long-winded canonical value MCMXCIX. In any case, nil nisi bonum mortuis. John Gilmore, Ashland, MA 01721 - USA ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
