User header labels

User header labels (UHLa) are optional, and there is no limit to the number that can be associated with a data set. They must contain only valid ASCII characters, but need not be sequentially numbered or lettered. These labels contain user-specified data that can be made available to your program for processing.

If you want the system to write user header labels or to make user header labels available to your program, you must specify AUL on the DD statement and the address of a user header label routine in the DCB exit list. (The exit list can address several user header label routines, that is, routines that process input user header labels and create output user header labels.) The DCB exit list is described in z/OS DFSMS Using Data Sets.