You're right guys : LTO Library's are supported since earlier versions, but
I couldn't get
our new IBM Ultrium Tape Library completely working without doing the
upgrade from 4.1.0 to
4.1.3 (which adds the lto devtype).
I could find this in the README File (and wrongly assumed LTO wasn't
supported before, but it is,
through the generictape devtype):  Sorry about that !

Nonetheless maybe it can still help some people :

Part of the readme file of the 4.1.3 update.

$$1 o Support for IBM LTO Ultrium (358x) devices

**********************************************************************
TSM supports the IBM 3580, 3581, 3583 and 3584 LTO Ultrium products on the
AIX, NT 4.0 and NT 5.0 platforms.
 - The IBM 3580 is a stand-alone drive.
 - The IBM 3581, 3583 and 3584 are automated libraries.

Users must use the SSD RMSS device drivers on these platforms to recognize
and configure the IBM 3580, 3581, 3583 and 3584.
To obtain the correct level of the device driver, review the README files
in the ftp.software.ibm.com/storage/devdrvr.

To define the device class, users should use the following:

   DEFINE DEVCLASS device_class_name DEVTYPE=LTO
                   FORMAT=[DRIVE or ULTRIUM or ULTRIUMC]
                   LIBRARY=library_name

NOTE: For RSM, the DEVTYPE is LTO instead of GENERICTAPE.  All other
devices will continue to be defined with DEVTYPE=GENERICTAPE.

On the AIX and NT 4.0 platforms, users should define the IBM 3581, 3583
and 3584 automated libraries as follows:

  DEFINE DRIVE library_name drive_name DEVICE=<device_special_file>
               ELEMENT=<element_number>

On Windows 2000 platform, users should define the IBM 3581, 3583 and 3584
automated libraries as follows:

  DEFINE LIBRARY library_name LIBTYPE=RSM MEDIATYPE="LTO Ultrium"

  Note that the quotes around "LTO Ultrium" are required.
  Users should use standard RSM configuration techniques.


Examples:

On AIX, assuming AIX recognized and configured the medium
changer as /dev/smc0 and the drive as /dev/rmt0:

  DEFINE LIBRARY 3584LIB LIBTYPE=SCSI DEVICE=/dev/smc0
  DEFINE DRIVE 3584lib rmt0 DEVICE=/dev/rmt0 ELEMENT=104


and so on ....