I did not reply to Charles Mills because I did not judge his post
interesting.
Let me, however, rehearse what I said originally at greater length. Coding
DUMMY has the effect that everything following it is ignored, no DCB
information is retained.
Coding DSN=NULLFILE,DCB=... permits NULLFILE to be overridden and the
retained DCB info to be used.
This is an old distinction, but it has not gone away. I have just verified
that it is still operational.
When in penance for my sins I have taught JCL I have in fact made it clear
that DUMMY has no legitimate uses outside straight-up old-style JCL punched
into 80-column cards, that it has no place in a procedure of either sort.
About citations of the obvious I grow less and less patient as I age. There
are days when I am still prepared to summon up arguments for the oblate
sphericity of the earth to confute some flat-earther, but there are other
days when I am not.
The JCL manual snippet quoted by Paul Gilmartin,
The system ignores all parameters other than DUMMY or
DSNAME=NULLFILE and DCB. The DCB parameter must be coded if you
would code it for normal I/O operations. ...
specifies just exactly the behavior I describe above. Moreover, it does so
in language that seems to me to be quite clear enough. In standard English
the boolean operator AND takes precedence over the boolean operator OR: 'A
or B and C' means '(A) or (B and C)'.
Expanded, this snippet thus means
o If you code DUMMY all else is ignored
o If you code DCB=NULLFILE, DCB information will be retained.
This expansion does not, however, seem to me to be necessary or desirable.
Those who cannot read should not write JCL.
Long ago Justice Holmes used the word 'relict' in an opinion, and when his
law secretary suggested that it was not perhaps very well known his now
legendary response was,
'May God twist my tripes if I will string things out for the delectation of
fools'.
This response was the right one. Dumbing down as a strategy doesn't work.
It produces only a descending spiral of ignorance.
John Gilmore
Ashland, MA 01721
U.S.A.
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