We are upgradeing the drives in our 3494 library to:
-double the storage capacity of the J cartridges
-convert from SCSI to fibre
-convert from SCSI to fibre
There seems to be a question of if we need to convert just one drive and There 
seems to be a question of if we need to convert just one drive and move the 
data to the newly defined lib / drive or can we simply convert both drives, as 
long as the drives remain in the same library defined to TSM.

Has anyone done this? The existing cartridges can be read by the upgraded 
drives ( but noit written to ). I guess the question is will TSM use the newly 
defined drives when a call for a cartridge with existing data is made.