"session marked for kill"
*Cause: The session specified in an ALTER SYSTEM KILL SESSION command
cannot be killed immediately (because it is rolling back or blocked
on a network operation), but it has been marked for kill. This
means it will be killed as soon as possible after its current
uninterruptable 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.