Disable all table constraints in Oracle

BEGIN
  FOR c IN
  (SELECT c.owner, c.table_name, c.constraint_name
   FROM user_constraints c, user_tables t
   WHERE c.table_name = t.table_name
   AND c.status = 'ENABLED'
   ORDER BY c.constraint_type DESC)
  LOOP
    dbms_utility.exec_ddl_statement('alter table ' || c.owner || '.' || c.table_name || ' disable constraint ' || c.constraint_name);
  END LOOP;
END;
/

BEGIN
  FOR c IN
  (SELECT c.owner, c.table_name, c.constraint_name
   FROM user_constraints c, user_tables t
   WHERE c.table_name = t.table_name
   AND c.status = 'DISABLED'
   ORDER BY c.constraint_type)
  LOOP
    dbms_utility.exec_ddl_statement('alter table ' || c.owner || '.' || c.table_name || ' enable constraint ' || c.constraint_name);
  END LOOP;
END;
/

set heading off

spool drop_constraints.out

select
    'alter table ' ||
    owner || '.' ||
    table_name ||
    ' drop constraint ' ||
    constraint_name || ';'
from
    user_constraints;

spool off

set heading on

@drop_constraints.out

SET Serveroutput ON
BEGIN
    FOR c IN
    (SELECT c.owner,c.table_name,c.constraint_name
    FROM user_constraints c,user_tables t
    WHERE c.table_name=t.table_name
    AND c.status='ENABLED'
    ORDER BY c.constraint_type DESC,c.last_change DESC
    )
    LOOP
        FOR D IN
        (SELECT P.Table_Name Parent_Table,C1.Table_Name Child_Table,C1.Owner,P.Constraint_Name Parent_Constraint,
            c1.constraint_name Child_Constraint
        FROM user_constraints p
        JOIN user_constraints c1 ON(p.constraint_name=c1.r_constraint_name)
        WHERE(p.constraint_type='P'
        OR p.constraint_type='U')
        AND c1.constraint_type='R'
        AND p.table_name=UPPER(c.table_name)
        )
        LOOP
            dbms_output.put_line('. Disable the constraint ' || d.Child_Constraint ||' (on table '||d.owner || '.' ||
            d.Child_Table || ')') ;
            dbms_utility.exec_ddl_statement('alter table ' || d.owner || '.' ||d.Child_Table || ' disable constraint ' ||
            d.Child_Constraint) ;
        END LOOP;
    END LOOP;
END;
/