>We will have to transfer the client data to the new machine. The
>problem we are facing is that we use 3490 tapes with OS/390 ADSM and
>3590 with the new AIX ADSM system and therefore have no tape export
>medium.

Matthias - Not an enviable situation.  The simplest solution might be
           if the interface type on the 3590s allowed them to be
connected to the OS/390 system for the duration of the Export, and
then reattach them to AIX for the Import.  Or you might be able to
borrow a DLT or the like (I perceive some customers eager to give
up their 3570s) for attachment to one system and then the other.
    Beyond that you *might* be able to use ADSMv3 features such as
Virtual Volumes to store the data on another server (from OS/390
to AIX) - see Chapter 13 of the v3 Admin Guide - and thus get the
data over there that way.  (I don't have the v3 experience to say
for sure.)
            Richard Sims, BU