A data transfer method for transferring data frames according to Fibre Channel Protocol between a first storage control unit and a second storage control unit in a remote copy system, wherein the remote copy system includes a first storage control unit, and a second storage control unit connected via a communication tool to the first storage control unit, that receives data from the first storage control unit. A buffer-to-buffer credit value applied to the data frame transfer is increased according to the distance between the first storage control unit and the second storage control unit.