How to kill? (Full rollback segment)

We are running:
Oracle7 Server Release 7.2.3.0.0 - Production Release With the distributed, replication and parallel query options The user is running PowerBuilder 4.

I suppose I can do a 'shutdown immediate' to solve my problem, but I hope there is another way around...

A user has a transaction that's stuck because of a full rollback-segment.
->1: Are there anything like a 'Kill transaction'-statement?

I tried to kill the users session, but the kill statement waits for the transaction to finish. (ORA-00031: session marked for kill)
->2: Are there anything like a 'Kill session immediate'-statement, that
will roll back the transaction?

I selected the Process attribute from the v$session view, my plan was to kill the users unix session.
This statement returned 9022:01, but using ps -ef in Unix I couldn't find such a process.
Are there any way to kill the user from the Unix-prompt?

Are there any way, except from 'shutdown immediate', to force a rollback on the active transaction before it has completed?

Are there any way to tell the transaction to continue, but using rollback segment R03 for the rest of the transaction?

Thanks in advance,
Njål Ekern

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Njål A. Ekern
n.a.ekern_at_usit.uio.no