Hey roy,

this does not sound like a problem with TSM.

Possible scenario:

create extra storage pools for Archives
(DiskA/primary, TapeA/secondary/NotCollocated and TapeB/backup)

point your archives into DiskA

run regular
        backup stg DiskA TapeB
        backup stg TapeA TapeB
        (the second one will usually do nothing,
        this is just for case your archive run is larger as DiskA)

each time a tape in TapeB becomes full, send it offsite and mark it as
offsite (upd vol ..).

regulary check status of tapes in TapeA, (q vol stg=tapeA)
checkout full ones out of library,
and keep them offline but onsite.

This way you have both offsite backups for case of fire etc.
and onsite backups for case of casual restores.

Another point: if you are going to keep tapes for 7-10 years,
you should consider refreshing them
(e.g. move data a_TapeFromTapeA DiskA)
How often you shall do it depends on technology you use.

best regards

Juraj Salak
Asamer Holding