set pages 999
select  s.sid, s.serial#, s.osuser, s.program, s.status, 
        decode(s.command, 
            1,'Create table' , 2,'Insert', 3,'Select' , 6,'Update',
            7,'Delete' , 9,'Create index', 10,'Drop index' ,11,'Alter index',
            12,'Drop table' ,13,'Create seq', 14,'Alter sequence' ,15,'Alter table',
            16,'Drop sequ.' ,17,'Grant', 19,'Create syn.' ,20,'Drop synonym',
            21,'Create view' ,22,'Drop view',23,'Validate index' ,24,'Create procedure',
            25,'Alter procedure' ,26,'Lock table', 42,'Alter session' ,44,'Commit',
            45,'Rollback' ,46,'Savepoint',  47,'PL/SQL Exec' ,48,'Set Transaction',
            60,'Alter trigger' ,62,'Analyze Table', 63,'Analyze index' ,71,'Create Snapshot Log',
            72,'Alter Snapshot Log' ,73,'Drop Snapshot Log',
            74,'Create Snapshot' ,75,'Alter Snapshot', 76,'drop Snapshot' ,85,'Truncate table',
            0,'No command', '? : '||s.command) nocommand
from v$session s
/

-- kill the session
alter system kill session 'sid,serial'


-- source: http://www.shutdownabort.com/dbaqueries/Administration_Session.php
-- last activity
set lines 100 pages 999
select username
,      floor(last_call_et / 60) "Minutes"
,      status
from   v$session
where  username is not null
order by last_call_et
/

-- last logon time
set lines 100 pages 999
col ID		format a15
col osuser	format a15
col login_time	format a14
select 	username
,	osuser
,	sid || ',' || serial# "ID"
,	status
,	to_char(logon_time, 'hh24:mi dd/mm/yy') login_time
,	last_call_et
from	v$session
where	username is not null
order	by login_time
/


-- open cursors
set pages 999
select 	sess.username
,	sess.sid
,	sess.serial#
,	stat.value cursors
from	v$sesstat stat
,	v$statname sn
,	v$session sess
where	sess.username is not null
and	sess.sid = stat.sid
and	stat.statistic# = sn.statistic#
and	sn.name = 'opened cursors current'
order by value;

    -- or this one
    set lines 100 pages 999
    select count(hash_value) cursors, sid, user_name from v$open_cursor
    group by sid,user_name order by cursors;