Processing time for job execution is shortened by using computation capability to the maximum extent possible.When a user makes a job request, the job request is sent from an LDS program of a first computer to a second computer; the second computer executes data preparation processing and empty area reservation processing with regard to a storage unit (disk A) and stores the results to an the FIFO of the first computer; when the output from the FIFO is transferred via a job release program to the LDS program, the transferred content is then transferred to a third computer; and the third computer selects a computer that should execute the job, from among a group of computers and commands the selected computer to execute the job.