Joined: 23 Nov 2006 Posts: 19270 Location: Inside the Matrix
If you specify DD DUMMY and read the file, it will raise the "at end" on the first read. If you write to a DD DUMMY, it does no/io, but the program runs as thought it was creating output. This can be handy if you need to run a program that has several outputs and you only need part of them - especially if an output is a very large report that is not needed for this particular run.
DD DUMMY is often used as a "place-holder" for clarification that there is as dataset used there and is overridden at execution with the actual DD information for the run.