Provided is a method of operating a phase change random access memory comprising a switching device and a storage node comprising a phase change layer. The method includes applying a reset current passing through the phase change layer from a lower portion of the phase change layer toward an upper portion of the phase change layer and being smaller than 1.6 mA to the storage node to change a portion of the phase change layer into an amorphous state. The set voltage is in an opposite direction is exemplary embodiments, and a connector is of small cross-sectional area.