Abstract: A data transmission method for transmitting data from a first processing unit having a relatively large memory capacity to a second processing unit having a relatively small memory capacity. The method has steps of (a) retrieving data stored in a first memory device, (b) storing in a temporary file only a record, from the retrieved data, relating to a predetermined time period including a current date; (c) determining whether or not the size of the temporary file is within the capacity of a second, smaller capacity, memory device; and (d) transferring the temporary file to the second processing unit in response to an affirmative result of the step (c), or not transferring the temporary file to the second processing unit in response to a negative result of the step (c).