Read and write considerations

Learn the read and write considerations for tape.

• Specify record lengths in your program when writing variable-length records (*D, *DB, *V, *VB, *VS, *VBS, or *U specified on the RCDBLKFMT parameter on the CRTTAPF command).
  If the maximum record length on tape is shorter than the output record length (because of overrides or existing file labels):

  • The system truncates the records to the maximum length that is allowed.
  • The system sends a diagnostic message when you open a device file to indicate that output records may be truncated.
• If the program specifies a record length that differs from the actual length of the data, the system pads or truncates the data to match the program specification.