5. The system according to claim 1 , wherein: the operation status of the second-tier server is any one of a normal status, a heavy-load status in which the second-tier server is in operation but requires a time equal to or more than a threshold value for processing, and an abnormal status in which the second-tier server is out of operation, and the table generator receives the operation status of second-tier servers, and evaluates each of the second-tier servers as being in the normal status on condition that a ratio of the operation statuses indicating that the second-tier server operates normally is equal to or more than a predetermined reference value.
5. The system according to claim 1 , wherein: the operation status of the second-tier server is any one of a normal status, a heavy-load status in which the second-tier server is in operation but requires a time equal to or more than a threshold value for processing, and an abnormal status in which the second-tier server is out of operation, and the table generator receives the operation status of second-tier servers, and evaluates each of the second-tier servers as being in the normal status on condition that a ratio of the operation statuses indicating that the second-tier server operates normally is equal to or more than a predetermined reference value. 6. The system according to claim 5 , wherein the table generator evaluates, as being in the heavy-load status, each of the second-tier servers not having been evaluated as in the normal status, on condition that a ratio of the operation statuses indicating that the second-tier server operates under heavy-load is equal to or more than the reference value.