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 each field of a label is explained in the description of label formats. The process of updating the JFCB is explained in Figure 1.

A security indicator of 0, 1, or 3 is set in the HDR1 label even if the volume is RACF defined. However, when the volume resides in an IBM automated tape library, the security indicator is always set to 0, indicating no password protection.

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