Data set characteristics

The HDR2 label immediately follows the HDR1 label. The system uses the HDR2 label to determine certain data set characteristics, if these characteristics are not otherwise specified by the user. The characteristics that can be obtained from the HDR2 label are:
  • Record format
  • Block length
  • Logical record length
  • Tape recording technique
  • Type of control characters
  • Coded character set identifier (CCSID)

The above information is obtained from the label and recorded in the job file control block (JFCB) and the data control block, provided that the appropriate fields in these control blocks contain zeros. The label information cannot override any characteristics previously specified in the processing program or the DD statement. For an explanation and illustration of this merging process, see Completing the data control block.

Parent topic: Processing the HDR2 label