I don't believe it matters whether you use readwrite or readonly, the
end result will be that your volmue gets deleted.  I have an
adminstrative schedule defined to update all volumes with a
wherestatus=empty to access=readonly.  You can do this whenever it fits
into your schedule; daily or weekly, at any time of the day you see fit.

I have never had a problem with something having a status of empty but
still having data on it.  I have seen situations where the %Util was
0.0, but there were still files on the tape.  I would go by the status
and not worry about it.

This whole process should be happening automatically for you onsite
tapes, but for the offsite tapes, the only automated way of doing this
is to use the DRM product.  But you still have to initiate scheduled
administrative commands to get it to do its thing as far as changing
the access to indicate tapes are leaving or coming back from your
offsite location.

Elvin Peterson
SC Johnson Wax
epeterso AT scj DOT com