User label processing

Understand the basics of how user labels work.

The system uses the USRLBLPGM parameter to specify the name of a program used to process user header and trailer labels. This parameter is not valid for save and restore functions.

The system calls the program, which the USRLBLPGM parameter specifies, for open and close processing, to process every label. The system calls the program one additional time to tell the program that there are no more labels.

Figure 1 shows the format of a tape with user labels. At open, the system will call the user-label program three times for processing the labels in the diagram. Those calls are for UHL1, UHL2, and a final time to indicate completion. At close, the system will call the user-label program three more times.

The system passes three variables to the program. The program variables have the following lengths:

• Parameter 1: 80 characters
• Parameter 2: 1 character
• Parameter 3: 244 characters

• Parameter 1
  Read this section to understand parameter 1 that is passed to the user label program.
• Parameter 2
  Read this section to understand parameter 2 that is passed to the user label program.
• Parameter 3
  Read this section to understand parameter 3 that is passed to the user label program.