PURPOSE: To minimize the interruption of on-line processing by storing fault information collected at the generation of the fault in a specific address area prevented from damage due to restart processing, and after completing the restart processing, transferring the fault information to an external storage device.

CONSTITUTION: When an important fault is generated in the system, a fault processing program is started and the fault information at the generation of the fault and control data of the program are stored in the specific address area 6 in a main storage 5 which is not destroyed by the restart processing except initialization at the connection of a power supply. Then, hardware is started to generate a reset signal. In the restart processing at the generation of the important fault, a processor 4 is started by the reset signal at first and then initializing for setting up the device 5 to an initializing memory pattern is executed. Subsequently, a restart processing program and an on-line processing program are loaded and the fault information in the area 6 is transferred to a fault information storing area 2 in the external storage device 1. The area 2 can store the fault information for a long period.