Format of IBM standard user label (UHL1 - UHL8 or UTL1

IBM standard user labels contain user-specified information about the associated data set. User labels are optional within the standard label groups.

Figure 1 shows the format of user labels. The format is used for user header labels (UHL1-UHL8) and user trailer labels (UTL1-UTL8). The labels are 80 characters in length. They are recorded in the density specified using JCL. Seven-track tape records are in BCDIC. The contents and processing of each field of the label are described below.

Figure 1. Format of user label

1—Label Identifier (3 bytes)

Contents: Three characters that identify the label are as follows:
- UHL
  
  User header label (at the beginning of a data set)
  
  UTL
  
  User trailer label (at the end-of-volume or end-of-data-set).
Processing: This field is read to verify that the record is a user label. The system accepts either UHL or UTL.

2—Label Number (1 byte)

Contents: The relative position of this label within a set of labels of the same type; it can be a number from 1 to 8.
Processing: This field is read to ensure that no more than eight user labels are processed. This field is read in conjunction with Field 1.

3—User Specified (76 bytes)

Contents: Specified by the user.
Processing: Specified in the DCB exit list.