I killed a session
ALTER SYSTEM KILL SESSION '123,456' IMMEDIATE;
But it remains in
v$session for 10 days, although an attached process is absent in
SELECT s.username, s.osuser, s.sid, s.serial#, p.spid FROM v$session s, v$process p WHERE s.sid = '123' AND p.addr (+)= s.paddr;
I've also checked all Linux processes related to Oracle and found no zombies: all present processes are consistent to alive sessions.
This happens not for all the killed sessions. It seems that PMON is active, because the most of the killed sessions are cleaned from the list in a reasonable time (often it takes a second).
What can be done to eliminate long-playing killed session from the list?