ORA-04021: timeout occurred while waiting to lock object

ORA-04021: timeout occurred while waiting to lock object 

LIBRARY CACHE LOCK HOLDERS ->

SELECT SID,SERIAL#,USERNAME,STATUS,SCHEMANAME,OSUSER,MACHINE,PROGRAM,SQL_ID
  FROM v$session
    WHERE saddr
    IN (  SELECT kgllkses
            FROM  x$kgllk lock_a
             WHERE kgllkmod > 0
AND exists (SELECT lock_b.kgllkhdl from x$kgllk lock_b
WHERE kgllkses IN (SELECT saddr FROM v$session WHERE event= 'library cache lock') /* blocked session */
AND lock_a.kgllkhdl = lock_b.kgllkhdl
AND kgllkreq > 0)
);

kamil.piorekk@gmail.com

Best regards /