DBMS_LOCK-paket
Detta kommer att göra vad du vill:
dbms_lock.allocate_unique('control_lock', v_lockhandle);
v_result := dbms_lock.request(v_lockhandle, dbms_lock.ss_mode);
...
v_result := dbms_lock.release(v_lockhandle);
http://download.oracle.com/docs /cd/B28359_01/appdev.111/b28419/d_lock.htm