Joined: 30 Nov 2013 Posts: 753 Location: The Universe
That's actually a good question. I, too, have occasionally been killed by unexpected DD DUMMY issues like the one you encountered. It seems to me input DD DUMMY shouldn't care since any input request is going to immediately raise end of data.
Output, on the other hand, does raise possible problems. Speaking in Assembler terms, DSORG=PS,MACRF=PL requires a pseudo I/O buffer since PUT returns a buffer address, where DSORG=PS,MACRF=PM does not because (hopefully) the access method is just going to return without moving anything.
I just spent some time hunting for a hint in DFSMS Using Data Sets and found nothing.
JCL Reference says
Code the DCB parameter, if needed. If the program does not supply all the data control block information, make sure that the DCB parameter supplies the missing information.
In other words, that's meaningless. How the [text deleted since terms inappropriate for the gentler gender and most children were used] is some poor shlub going to answer this!