PURPOSE: To improve both operability and controllability by ensuring an automatic control procedure for open/close of the session between a terminal and a host computer in an on-line processing mode.

CONSTITUTION: When an instruction is given to a job processing system 5 at the side of a terminal 4 via an input/output device 6, a job processing program 13 is started and a session control information read processing part 14 reads the session control information. Based on such control information, the session is opened between a communication system 3 and job processing systems 2aW2n respectively. Then a job data processing part 16 starts the job processing. When an end instruction is supplied for the job processing, a session close processing part 17 closes the session between the system 3 and the systems 2aW2n respectively.