In a recent note, john gilmore said:
> Date: Fri, 27 May 2005 22:35:28 +0000
>
> 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
>
I agree with your derivation from the UG. However, a simple
experiment shows the statement to be grossly wrong. The job
output fragment:
3 //STEP EXEC PGM=IEFBR14
//*
4 //SYSUT1 DD DUMMY,DISP=SHR,PATHOPTS=ORDWR
4 IEFC009I KEYWORD PATHOPTS IS MUTUALLY EXCLUSIVE WITH
KEYWORD DISP ON THE DD STATEMENT
This demonstration severely erodes the credibility of the UG: it's
impossible to have a conflict between parameters which are "ignored".
I'll presume further experiments are necessary to manifest the facts.
> 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.
>
I'll take that cum grano salis. "Dumbing down" is an effective
pedagogic strategy. And here, a little stringing out could have
added value in clarity exceeding the cost of the verbosity:
If you code DUMMY, all other parameters are ignored; if you
code DSN=NULLFILE all other parameters except DCB are ignored.
... an accurate paraphrase, except for the experimental refutation.
But "standard English" lacks mathematical rigor: an alternative
paraphrase might be:
If you code DUMMY, all other parameters are ignored; if you
code both DSN=NULLFILE and DCB, all parameters other than those
two are ignored.
... in other words, if you code DSN=NULLFILE absent DCB, other
parameters are not ignored.
> o If you code DCB=NULLFILE, DCB information will be retained.
^^^
"DSN" (editorial correction -- gil)
>
The "and" operator is mathematically commutative. Is this likewise
true in "standard English"? What of the putative paraphrase:
The system ignores all parameters other than DUMMY or
DCB and DSNAME=NULLFILE. The DCB parameter must be coded if you
would code it for normal I/O operations. ...
By a derivation parallel to yours above, this results in:
o if you code DCB information, DSN=NULLFILE will be retained.
if you code DCB, all additional parameters other than DSN=NULLFILE
are ignored. I'm rapidly convincing myself that the text needs
stringing out. I know, I'm engaging in pedantry, but, PKB.
-- gil
--
StorageTek
INFORMATION made POWERFUL
----------------------------------------------------------------------
For IBM-MAIN subscribe / signoff / archive access instructions,
send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO
Search the archives at http://bama.ua.edu/archives/ibm-main.html
