Thank you to those who have responded - perhaps a little clarification is
needed from me as to why we are doing this. Our customer has 8 very large
HP-UX boxes being backed up by a a small 3-year old IBM RS/6000 with IBM
3494 library and 3590E drives. The RS/6000 needs upgrading - memory, RAID
disk, Gigabit LAN, CPU speed etc. etc., so a new machine is the most
effective way. But they have a spare HP-UX box so have requested we use that
for TSM (it's got 8 CPUs, 8 Gb memory, EMC RAID disk etc. vs. 2 CPUs, 512 Mb
memory, SSA (non-RAID) disk on the RS/6000). Hence the plan to move from AIX
to HP.  Yes I would prefer a shiny new RS/6000 but the customer doesn't see
the need to shell out when he has a very good spare box that supports TSM.

We will be taking the 3494 with us using the dual-SCSI interfaces to cable
both systems for the transitional period. So my question is how do we
achieve this? The options seem to be to install the same TSM patch level on
both processors and then

*       Quiesce the AIX, empty and delete disk pool volumes, run a BACKUP DB
and then a RESTORE DB
*       As above but shut down to do a DUMPDB and then a LOADDB.
*       As above but do an UNLOADDB and then a LOADDB ( Database is 27 Gb,
43m versions - how long does this take?)
*       Start the HP as new and empty, and allow the AIX service to expire
after 90 days. This we know will work but 3494 capacity becomes an issue.
Archive data would have to be exported and imported, though.

Export/Import of node data is not possible - we have 23 Tb of it and
customer doesn't expect an outage that long! IBM tell me export/import of
node data is the only supported method, which must imply 3590 tapes written
on the AIX system must be readable on the HP-UX system.

Anyone got any further thoughts?

Many thanks