> > How does one properly retension a tape on a TKxx transport?

.....

> Maybe just read through it to the end and do a rewind?

That does not often work.  If it does, then the retension was not
really needed.  When the read stops in mid tape, with what apparently
is a dragging of the tape (e.g., sticking of the tape layers together,
as seems to be happening on the older tapes), I need something to force
a high-speed tape movement.  A usual dd/tar/whatever read does not do
that at high speed, in a continuous, forceful movement.  Mt appears
to do that since it is just throwing away bits after reading.  Mt
appears to spin the tape at maximum speed, thus giving it more
momentum to get across the places where it is sticking slightly.
This is after observing the actual tape movement on an open transport.
A retension would be best, since it does not read anything from the
tape, except look for the hardware end of tape.  But, DEC's wisdom
did not seem to include that capabilty in the DLT transport
mechanisms.  IFF there IS as way to do that, I want to find
out how.  Retensioning seems to be something overlooked in the
DLT tapes, but maybe be important for tapes that have sat for
years unused.

Thanks

Bob