On Tue, 11 Nov 2008 09:27:09 -0600, Staller, Allan wrote:
>It is, but it fools the converter/interperter into thinking there really
>is a dataset there and allows the concatenation to proceed, as opposed
>to DD DUMMY which "truncates" the concatenation.
>
I remain open to persuasion, although John G. failed to persuade me.
What do you mean by "truncates" the concatenation, not at execution
time. I might imagine that you mean that catenands after DUMMY
are not processed by the convertor/interpreter (except for a syntactic
scan, necessarily). So no TIOT entry would be built for catenands
after DUMMY. However:
//STEP1 EXEC PGM=IEFBR14
//SYSUT1 DD DUMMY
// DD DISP=SHR,DSN=NO.SUCH.DATASET
results in:
IEF212I DUMMYCAT STEP1 SYSUT1 +001 - DATA SET NOT FOUND
IEF272I DUMMYCAT STEP1 - STEP WAS NOT EXECUTED.
It appears to me that the concatenation was not "truncated".
It's frustratingly ironic that the job fails if the data set
can not be allocated, but does not process it when it can be
allocated.
I'm still interested in seeing a pair of examples where the
behavior of DUMMY differs from that of DSN=NULLFILE.
>Agreed, the effect at execution time is the same.
>
As a programmer, I care much about the effect at execution time,
and hardly at all about subtle, almost unobservable, behavior
internal to the C/I.
-- gil
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