Often an Administrator needs to list all connected users to be able to afterwards to kill the session. The problem when you kill the session is that it is possible that on the operating system level the process remains active. With the following script you can list all connections and obtain the information to terminate the session on Oracle level but also on the operating level as it will show you the process ID.
REPHEADER ON
SET LINES 150
SET PAGESIZE 100
COLUMN SPID FORMAT 99999 HEADING 'SYSTEM PID'
COLUMN SID FORMAT 99999 HEADING 'SID'
COLUMN SERIAL# FORMAT 999999 HEADING 'SERIAL#'
COLUMN USERNAME FORMAT A15 HEADING 'USERNAME'
COLUMN MACHINE FORMAT A15 HEADING 'MACHINE'
COLUMN OSUSER FORMAT A20 HEADING 'OS USER'
COLUMN PROGRAM FORMAT A15 HEADING 'PROGRAM'
select p.SPiD, s.SID , s.SERIAL# , s.username, s.PROGRAM, s.machine, s.osuser from v$session s, v$process p
where (s.username is not null) and (s.paddr=p.addr)
order by s.username, s.osuser;