HIGH RELIABILITY SYSTEM

PURPOSE:To efficiently use a real machine by connecting an input/output device connected to an opposite side to its own real computer when the real computer fails to operate at the opposite side, and making perform an operation handled with a virtual computer in the real computer at the opposite side, with the virtual computer controlled at its own side. CONSTITUTION:When a real computer 1 fails to operate, a virtual computer monitor 21 at a real computer 2 side can recognize the down of the real computer 1 because the periodical sending of a bit of information from the real computer 1 to the real computer 2 is ceased. When the real computer 1 fails to operate,a system switching part 23 at the real computer 2 side issues a command to switch I/O devices 5 and 6 to the real computer 2 side. And the virtual computer monitor 21 allocates the I/O devices 5 and 6 to a virtual computer 25-2, and informs the fact that the virtual computer 25-2 operates as a main system for the I/O devices, then making operate the virtual computer 25-2. The virtual computer 25-2 performs the initialization of a communication control program, and restarts the operation setting an operation A'' in an operation possible state, and the virtual computer 25-2 as the main system. In this way, a high reliability system in which the real machine can be used efficiently can be obtained.