KILL Sessions on NT - Error 00031

Trying to kill a session thus:

alter system kill session '17,3895'
*
ERROR at line 1:
ORA-00031: session marked for kill

And V$SESSION still shows the session. Whats happening?

OK ...

ORA-00031 session marked for kill

Cause: The session specified in an ALTER SYSTEM KILL SESSION command cannot be killed immediately because the session is involved in a non-interruptible operation (for example, rolling back a transaction or being blocked by a network operation). The session has been marked to be killed as soon as possible after the current operation is done.

Action: No action is required for the session to be killed, but further executions of the ALTER SYSTEM KILL SESSION command on this session may cause the session to be killed sooner

So - question is ... How do I discover what the non-interruptible operation is? The session was an application session that's a day old. I don't know the app so I can't guess what it might be doing?

joining v$session & v$sqlarea shows the session to be issuing a SELECT * from a view. So ... its not likely to be locked by a ROLLBACK is it?

Any ideas anyone?

another way to kill as session

Read note 69882.1 on metalink

HTH
Gert