I like this name (REPLACE instead of CREAT[E]). Prior to realizing that this
behavior is supported with UNIX files I had pondered long and hard about the
value. RENEW seemed OK, but I bit of a reach. CREAT[E] is based on the
existing OCREAT, but REPL[ACE] could work just as well.
I had a thought after I wrote the original post with regard to the actual
behavior of TRUNC. If it was based on the behavior of OTRUNC it would just
truncate the file. But in order to work more similarly to the two step "delete
and define" behavior, perhaps it should work that way. This would specifically
be desirable if the file attributes need to be changed. For example, if the
LRECL changes (in the program) and TRUNC didn't actually "delete and define"
the file then there would be a file attribute mismatch. But if TRUNC does do
"delete and define" (and the LRECL is not specified on the JCL, but gets it
from the program) then no JCL would need to be changed.
So the question in my mind is, should there be options for both behaviors, or
should TRUNC (or whatever) always do an implicit DELETE and an implicit NEW? I
don't see any harm in the latter, but I could be missing a use case.
Frank
________________________________
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> on behalf of
Paul Gilmartin <0000000433f07816-dmarc-requ...@listserv.ua.edu>
Sent: Friday, June 30, 2017 12:37 PM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: Possible RFE for new DISP JCL parameter options
On Fri, 30 Jun 2017 11:24:18 -0700, Charles Mills wrote:
>YES!!!
>
>Years ago I wrote and my company sold a mainframe-PC file transfer product
>(in the pre-FTP days), and it supported a DISP operand for the creation of
>mainframe datasets that worked exactly as you describe, with two steps under
>the covers. I'm trying to remember the keyword for the specification.
>Perhaps CREATE. It made sense then (1989) and it makes sense today.
>
Many desktop editors call this REPLACE; SAVE fails for an existing file.
>(It also did a kind of extended SDB under the covers. You could specify any
>one or two of LRECL, RECFM and BLKSIZE and it would intuit the others. Had
>an algorithm that made intelligent guesses. Specify RECFM=FB,BLKSIZE=8000 it
>would give you LRECL=80. Specify LRECL=137,BLKSIZE=8000 and it would give
>you RECFM=VB.)
>
What might it do for RECFM=FB,BKLSIZE=10640 (which happens to be 133 * 80).
526 $ factor 10640
Factors of 10640 are 2 2 2 2 5 7 19
It's ambiguous for any number with 2 or more prime factors.
-- gil
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