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
