Writing data set header labels

When the tape is accepted by the system for output, the system creates the header labels (HDR1 and HDR2) for the new data set. These labels are created from information in the updated JFCB and other system control blocks.

The source of information for the label fields is explained in the description of the label formats. The process of updating the JFCB is explained in Figure 1.

The security indicator is set in the HDR1 label even if the volume is RACF defined, unless the volume resides in an IBM automated tape library in which case there is no password protection.

If no user header labels are to be written, the system writes a tape mark after the HDR2 label. The tape is then ready to receive the new data set.