Jon LaBadie wrote:

There is an implied assumption in the chg-disk script that the virtual
tapes will be online at all times.  This comes from the line:

   LASTSLOT=`amgetconf$SUF tapecycle`

In tape changer scripts like chg-mtx the last slot and tapecycle are
not linked.

You might submit a Request For Enhancement to divorce these two parameters
in a revised chg-disk script.  Then your changer directory could contain
just the 20 mount point directories of the removable disks, or symbolic
links to those directories

That's already done in the latest amanda snapshot.
chg-disk read a changer config file, you can set LASTSLOT in that file.

Jean-Louis