PURPOSE: To provide a function for automatically executing a program while selecting the time point and equipment of a low load rate.

CONSTITUTION: Since a service processor 3 is provided with a means to monitor the load of a computer system, the load conditions of respective elements constituting the computer system such as a central processing unit (CPU) 1 and input/ output devices 4-6 are monitored and when the load is made lower than a fixed standard or when the state of lowering the load rather than the fixed standard is observed continuously for fixed time, it is judged that a diagnostic program can be executed so as to start the diagnostic program by sending the starting request of the diagnostic program to the CPU 1 together with a program name and a parameter previously registered on the service processor 3. Thus, the program can be executed without depending on human aid, and the other program executed on a data processor is not affected.