CREATE OR REPLACE TRIGGER save_our_db_user
BEFORE drop
ON database
BEGIN
    IF ora_dict_obj_type IN ('USER')       AND (sys_context('USERENV', 'HOST') not  IN ('paynode1','paynode1'))   THEN
        raise_application_error(num => -20003,   msg => 'you can not allow to DROP USER ' || ora_dict_obj_name ||   '!');
    END IF;
END ;
/