A technique is desired that can output a warning to a user before a buffer of a controller runs out of a free space. A control apparatus includes a buffer for buffering log data sequentially generated, an interface unit connectable with an external storage device, a writing unit for sequentially reading the log data buffered to the buffer and sequentially writing the log data to the external storage device while the external storage device is connected to the interface unit, a monitoring unit for monitoring a free space of the buffer, and a warning unit for outputting a warning upon the free space falling below a prescribed value.

A technique is desired that can output a warning to a user before a buffer of a controller runs out of a free space. A control apparatus includes a buffer for buffering log data sequentially generated, an interface unit connectable with an external storage device, a writing unit for sequentially reading the log data buffered to the buffer and sequentially writing the log data to the external storage device while the external storage device is connected to the interface unit, a monitoring unit for monitoring a free space of the buffer, and a warning unit for outputting a warning upon the free space falling below a prescribed value.