HP C7401A - SureStore Ultrium 230 Tape Drive Technical Reference Manual page 19

The
operating system, where 0 is the first device, 1 is the second and so on.
Normally, the drive repositions the tape to BOT (Beginning of Tape) when the
Rewind on Close
device file is closed. Using the no rewind option is useful when creating and
reading tapes that contain multiple files.
Retensioning consists of winding to EOT (End of Tape) and then rewinding to
Retension on Open
BOT, in order to reduce errors. If this option is selected, the tape is positioned
at BOT as part of the open process.
Compression can be disabled or enabled.
Compression
in the filename is the instance number assigned to the drive by the
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IBM (AIX) 19