anchor.diff:                                        {Pid, 0}
                                 end,
               ToDo = case LastUser of
  -                Pid ->
  +                ToUpdate when ToUpdate =:= Pid; ToUpdate =:= non ->
  +                    % check for create/delete race
                       case Op of
                           delete ->
  -                            ok;
  +                            case datastore:get(Level, ModelName, Key) of
  +                                {ok, SavedValue} ->
  +                                    {ok, save, [SavedValue]};
  +                                {error, {not_found, _}} ->
  +                                    ok;
  +                                GetError ->
  +                                    {get_error, GetError}
  +                            end;
                           _ ->
                               case datastore:get(Level, ModelName, Key) of
                                   {ok, SavedValue} ->
  
positive.code:         case LastUser of
              Owner ->
                  true;
              _ ->
                  false
          end
      end,
      delete(Level, Uuid, Pred).
  
  %%--------------------------------------------------------------------
  %% @private
  %% @doc
  
negative.code:                 Other ->
                      Other
              end,
              ok = case Ans of
                       ok ->
                           end_disk_op(Uuid, Pid, ModelName, Op, Level);
  