How to find out which user is running what sql query in oracle database

Below script will gives the information of

• Which user currently logged on
• Which sql query they are running
• Which computer the user is logged on
• How long the query is running

To run this query you need SELECT_CATALOG_ROLE or SELECT ANY DICTIONARY grant.

SELECT 
SUBSTR(SS.USERNAME,1,8) USERNAME,
SS.OSUSER "USER",
AR.MODULE || ' @ ' || SS.machine CLIENT,
SS.PROCESS PID,
TO_CHAR(AR.LAST_LOAD_TIME, 'DD-Mon HH24:MM:SS') LOAD_TIME,
AR.DISK_READS DISK_READS,
AR.BUFFER_GETS BUFFER_GETS,
SUBSTR(SS.LOCKWAIT,1,10) LOCKWAIT,
W.EVENT EVENT,
SS.status,
AR.SQL_fullTEXT SQL
FROM V$SESSION_WAIT W,
V$SQLAREA AR,
V$SESSION SS, 
v$timer T
WHERE SS.SQL_ADDRESS = AR.ADDRESS
AND SS.SQL_HASH_VALUE = AR.HASH_VALUE
AND SS.SID = w.SID (+)
AND ss.STATUS = 'ACTIVE'
AND W.EVENT != 'client message'
ORDER BY  SS.LOCKWAIT ASC, SS.USERNAME, AR.DISK_READS DESC
;