On Mon, 19 Feb 2018 20:14:29 +0000, Jesse 1 Robinson wrote:
>I can't speak for BPXWDYN, but I remember when REUSE became available in TSO.
>Before that, a CLIST writer (this was before REXX was ported to TSO) had to
>code like this:
>
>CONTROL NOMSG
>FREE DD(like-I-care-if-it's-allocated)
>CONTROL MSG
>ALLOC DD(now-I-want-it) ...
>
>This was necessary because if the DD was not already allocated, a gratuitous
>FREE would give the user a snarky message to that effect.
>
I recall an era when FREE of an unallocated DDNAME was fatal to the CLIST
(of course, the programmer should know better!) but ALLOCATE of a DDNAME
in use merely gave a snarky message. So, I resorted to:
ALLOCATE (like-I-care)
FREE
ALLOCATE (now-I-want-it).
RTDDN was a boon. I still shudder when I see programmers using RANDOM() to
generate DDNAMEs and hoping for the best.
>With REUSE, the allocation would take place with no distraction to the user
>either way.
>
For many years, REUSE did not work for UNIX files (it's better now). I think
there
was some semantic confusion about the overloading of "REUSE" and UNIX
allocations
could never be reused (like-I-care). For some of the interim, BPXWDYN
development
generously added an internal FREE when the programmer coded REUSE.
>The result was the *same* DD allocated to the data set(s) desired. This goes
>back to around 1980 +/-.
>
But I believe that the OP wanted the *same* data set allocated to two different
DDNAMES, or at least not to disrupt the existing allocation, and allocation
conversion or the REUSE option thwarts that.
I don't know the meaning or the intent of allocation conversion, except that
it's a PITA.
-- gil
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