In the case of OS/390 you are running the OAM task which has an exit that
may help.

Every system gets notification of a volume when it is inserted that is
registered to the 3494, even an open systems lmcpd system.  The OS/390
system is the only one that responds unfortunately.  It sets the category of
the tape based on whether the exit says to accept the tape or not.  For
OS/390 we implemented the exit and ignore tapes not for it by volser range.
Sorry, that does not help in TSM or AS/400.

What we desperately need from 3494 development is a lmcpd connection task
delivered for each platform that we can invoke a script from.  Then, we can
write the script in whatever tool we want.  That way you could dynamically
checkin under TSM and under an AS/400 do whatever it needs such as give the
tape a category via the mtlib command.

I believe that TSM will only label tapes that are in its categories already
or the FF00 category (insert), so you can make it skip the OS/390 tapes by
using the OAM exit.  I know TSM will not relabel that already has a valid
TSM label on it.  This is to prevent destroying tapes that have valid data.

If I could spend enough time to tinker around with C, I would write the code
for this task.  It is relatively simple.  And, essentially, you do not need
to run it but in one place because every host gets notified for all inserts.
And, by the way, the library represents the list of tapes in insert status
every time a host opens the interface to the library.