PL/SQL Giving sys.DBMS_LOCK Execution Permission To a User

To be able to use sys.dbms_lock a user should have been granted execution.

begin
 DBMS_LOCK.Sleep( 60 );
end;
PLS-00201: identifier 'DBMS_LOCK' must be declared

To grant execution to user:

grant execute on <object> to <user>;

sqlplus / as sysdba

grant all on sys.dbms_lock to user;