unique key 1 : col1, col2, col3
unique key 2 : col1, col2, col3, col4

Insert into tab1 (col1, col2, col3, col4) values (1,2,3,4);

select a.sid, a.serial#,sql_id ,(case LOCKED_MODE when 0 then 'none'
when 1 then 'null'
when 2 then 'row-S'
when 3 then 'row-x'
when 4 then 'share'
when 5 then 'S/Row-X'
when 6 then 'exclusive'
end ) LOCKED_MODE
from v$session a, v$locked_object b, dba_objects c
where b.object_id = c.object_id
and a.sid = b.session_id;

SELECT a.sid, 
       a.serial#, 
       sql_id, 
       ( CASE locked_mode 
           WHEN 0 THEN 'none' 
           WHEN 1 THEN 'null' 
           WHEN 2 THEN 'row-S' 
           WHEN 3 THEN 'row-x' 
           WHEN 4 THEN 'share' 
           WHEN 5 THEN 'S/Row-X' 
           WHEN 6 THEN 'exclusive' 
         END ) LOCKED_MODE 
FROM   v$session a, 
       v$locked_object b, 
       dba_objects c 
WHERE  b.object_id = c.object_id 
       AND a.sid = b.session_id; 

ORA-02049: timeout: distributed transaction waiting for lock

select owner, object_name, object_type from dba_objects where object='FIL_INFO';