...
>ANS1809W Session is lost; initializing session reopen procedure.
>
>appears almost constantly during backups. ...

I should think you would have TCP error indications aplenty in the TSM error log
on the AIX which should give some indication of the nature of the problem.

I would start by running an 'iptrace' on that AIX client, and then get your
network people involved to run a network line trace, which should show what's
wrong.  If going across a router between client and server, and if the client
is multi-homed, may play a part in the problem.

If this is the only AIX client among multiple having this problem, then you have
a basis for problem comparision: what's different about that client in terms of
its TSM config, AIX network config, network hardware, etc.  If no other AIX
client systems, perform the same client work in the AIX server system and
compare that.

I would hope that in your work with TSM Support that a client trace has also
been done: if not, pursue that for indications.

   Richard Sims, BU