On Thu, 23 May 2024 22:24:06 -0500, Mike Schwab wrote:
>
>VSAM came from the Future Systems development as a complete
>replacement, Lynn Wheeler has posts about that.
>It was cut back to be an addition to MVS, then combined with CVOL
>catalogs to ICF.
>
"complete replacement" of what, specifically? I have heard the
assertion that VSAM was intended to replace all other access
methods: QSAM, BSAM, BPAM, ...
I have known an OS partisan to rant hereabouts:
The MVS catalog tells the OS exactly where a data set resides,
whereas with UNIX the programmer must supply such information
to access any file.
I believe he was referring to pathnames.
I have never felt that hardship. UNIX provides alternative facilities:
o Mounted filesystems
o Symbolic links
o Directory hierarchy
o The current working directory
o Logical filesystems comprising multiple physical volumes,
a technique MVS never mastered, partly because of
compatibility constraints with BBCCHHR. It was desigh
shortsightedness to expose low-level DASD characteristics
to high-level programmers.
Beyond that, the MVS namespace is woefully small; another
archaic and insuperable compatibility constraint.
--
gil
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