Abstract: Even when a client unit 2 can not connect with a server unit 1, by comparing a system information held by a system information file 23 with the present status, a self-diagnosis is performed by a self-maintenance system file 24 of the client unit 2 itself, and as a result, when abnormality has occurred, the client unit 2 independently carries out recovering processing in accordance with its own backup file 25. When it is possible to connect with the server unit 1, the necessary information is obtained from the server unit 1 to carry out recovering processing and system update processing. By this processing, the following problem is settled: In case of an obstacle to the client in the conventional client/server system which is based on the premise of it being normally connectable with the server, when it becomes impossible to connect to a server, the client is prevented from downloading from the server the files necessary for maintenance processing.