ORA-04021: Timeout occurred while waiting to lock object

When developer is trying to recompile PL/SQL package, session hangs until get this error:

ORA-04021: timeout occurred while waiting to lock object

Basically, while someone or something else (a scheduled job perhaps?) is executing the package, then you won’t be able to perform the recompile. To get around this, you need to identify the locking session and kill it.

Executing this script as SYS (or another user with the appropriate privileges) will prompt you for the package name and reveal the culprit(s):

SELECT s.sid,
       l.lock_type,
       l.mode_held,
       l.mode_requested,
       l.lock_id1,
       'alter system kill session '''|| s.sid|| ','|| s.serial#|| ''' immediate;' kill_sid
FROM   dba_lock_internal l,
       v$session s
WHERE  s.sid = l.session_id
AND    UPPER(l.lock_id1) LIKE '%&package_name%'
AND    l.lock_type = 'Body Definition Lock'
/

NOTE: If your dba_lock_internal view doesn’t exist, you can create this by running: $ORACLE_HOME/rdbms/admin/catblock.sql
check what is doing this session

SELECT s.sid,
       NVL(s.username, 'ORACLE PROC') username,
       s.osuser,
       p.spid os_pid,
       s.program,
       t.sql_text
FROM   v$session s,
       v$sqltext t,
       v$process p
WHERE  s.sql_hash_value = t.hash_value
AND    s.paddr = p.addr
AND    s.sid = &session_id
AND    t.piece = 0 -- optional to list just the first line
ORDER BY s.sid, t.hash_value, t.piece
/

run kill command from the output of first script

alter system kill session 'SID,SERIAL#' immediate;

after that developer can recompile package.