How do I copy DAT tapes?

If you have two drives try tcopy(1). Otherwise the traditional UNIX
approach is ( dd if=/dev/rmt0 bs=1024b | dd of=/dev/rmt1 bs=1024b )
Put that in a while loop using a non-rewinding device to do multiple
files. To use drives from two different machines either get the GNU
dd (bundled with GNU tar) or use something like.

$ dd if=/dev/rmt0 bs=1024b | rsh hostname dd of=/dev/rmt0 bs=1024b