Some usefull TIPS

USER idle time

SELECT sid, osuser, username, status,
TO_CHAR(logon_time, 'DAY HH24:MI:SS') LOGON_TIME,
FLOOR(last_call_et/3600)||':'||
FLOOR(MOD(last_call_et,3600)/60)||':'||
MOD(MOD(last_call_et,3600),60) IDLE, program
FROM v_$session
WHERE username IS NOT NULL
ORDER BY last_call_et;

USER temp tablespace

SELECT username, default_tablespace, temporary_tablespace
FROM dba_users
ORDER BY 1;

USER informations

SELECT u.username, u.default_tablespace, 
u.temporary_tablespace "TMP TBS", u.profile, r.granted_role,
r.admin_option, r.default_role
FROM sys.dba_users u, sys.dba_role_privs r
WHERE u.username = r.grantee (+)
GROUP BY u.username, u.default_tablespace,
u.temporary_tablespace, u.profile, r.granted_role,
r.admin_option, r.default_role;

Create user sample

CREATE USER username
IDENTIFIED BY password
DEFAULT TABLESPACE tablespacename
TEMPORARY SPACE temp_tablespacename
QUOTA UNLIMITED ON tablespacename; 

GRANT CONNECT TO username;
GRANT RESOURCE TO username;

Active Processes(DBA)

SET pagesize 55;
SET linesize 170;
col SQL format a80;
col SERVER heading 'SVR' format a3;
col EVENT heading 'WAITING' format a30 fold_after;
col OSUSER heading 'OSUSER' format a8;
col USERNAME heading 'USERNAME' format a8;
col PID heading 'OSPID' format 99999;
col DISK_READS heading 'DISK I/O' format 99999999;
col BUFFER_GETS heading 'BUFFER|GETS' format 99999999;
 
SELECT  SUBSTR(V$SESSION.USERNAME,1,8) USERNAME,
     V$SESSION.OSUSER OSUSER,
--        DECODE(V$SESSION.SERVER,'DEDICATED','D','SHARED','S','O') SERVER,
     V$SQLAREA.DISK_READS DISK_READS,
     V$SQLAREA.BUFFER_GETS BUFFER_GETS,
        SUBSTR(V$SESSION.LOCKWAIT,1,10) LOCKWAIT,
     V$SESSION.PROCESS PID,
     V$SESSION_WAIT.EVENT EVENT,
        V$SQLAREA.SQL_TEXT SQL
FROM    V$SESSION_WAIT, V$SQLAREA, V$SESSION
WHERE   V$SESSION.SQL_ADDRESS = V$SQLAREA.ADDRESS AND
     V$SESSION.SQL_HASH_VALUE = V$SQLAREA.HASH_VALUE AND
        V$SESSION.SID = V$SESSION_WAIT.SID (+) AND
     V$SESSION.STATUS = 'ACTIVE' AND
     V$SESSION_WAIT.EVENT != 'client message'
ORDER BY V$SESSION.LOCKWAIT ASC, V$SESSION.USERNAME;

Kill Session

SELECT SID, SERIAL#
FROM V$SESSION
WHERE USERNAME = 'LSHR';

ALTER SYSTEM KILL SESSION '7,15';