Abstract: This paper analyses the active state number of a double-computer system which is reconfigurable at module level and compares it with other redundance configuration computer system which are spare standby at system level.The results show that the lower the redundance level is,the higher the reliability is,and the larger the active state number is. It will increase the complexity of management software. This paper introduces the design principles of management software and briefly discribes the features of some subroutiness

Key words: Active state, Computer, Fault tolerant technique, System management, System program