Disabling all oracle DB constraints of all tables

Just run the following plsql block.

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|| ' cascade');
  END LOOP;
END;
/