The rmt Special Files are

Special File Name | Rewind-on-Close | Retension-on-Open |   Bytes per Inch
==================+=================+===================+===================
/dev/rmt0         |       Yes       |         No        | Density Setting #1
/dev/rmt0.1       |        No       |         No        | Density Setting #1
/dev/rmt0.2       |       Yes       |        Yes        | Density Setting #1
/dev/rmt0.3       |        No       |        Yes        | Density Setting #1
/dev/rmt0.4       |       Yes       |         No        | Density Setting #2
/dev/rmt0.5       |        No       |         No        | Density Setting #2
/dev/rmt0.6       |       Yes       |        Yes        | Density Setting #2
/dev/rmt0.7       |        No       |        Yes        | Density Setting #2

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The two most common tctl commands are rewind & rewoffl (rewind & unload).

tar & tctl default to using /dev/rmt0

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To read the EBCDIC standard label from a tape, try

  tctl -f /dev/rmt2 rewind
  dd if=/dev/rmt2 count=1 conv=ascii

What you get back is
VOL1000295              ...            0+1 records in.
0+1 records out.

The 6 characters after the "VOL1" is the label, 000295 in this case.