>I have 3000 clients (each 5GB approx) backup proposal to TSM server.
>Expecting 600 to 1000 clients fire their  backup to TSM concurrently.  Can
>TSM able to handle all these session fired at a time ? ...

TSM has a 'Set RANDomize' server parameter which will amortize the impact
of so many clients in a given time window.
After the initial backup of the clients, most of the load will be in the
clients pulling the Active files list from the server, and then running
through their file systems in an Incremental backup: there will probably
be relatively few files from each client to be backed up.
You will probably want to implement a hierarchy with a large disk pool
ahead of a tape storage pool, as it's infeasible for each client to back
up directly to tape.  The Admin Guide manual lays that out.

I think, in light of recent discussions on the List, that we're all
wondering about your company affording that many client licenses.  :-)

   Richard Sims, BU     http://people.bu.edu/rbs