1. A system comprising: a plurality of dispatcher apparatuses which dispatch a transaction request by an external terminal apparatus; a plurality of first-tier servers which process the dispatched transaction request; and a second-tier server which processes a part of the transaction request in response to a request received from a first-tier server; wherein each of the dispatcher apparatuses comprises: a dispatcher storage device which stores a status table indicating an operation status of the second-tier server; a transferring unit which transfers a transaction request received from the external terminal apparatus to the first-tier server selected from the plurality of first-tier servers, in order to dispatch the requested transaction; a table generator which receives the operation status of the second-tier server included in a transaction response corresponding to the transferred transaction request, which evaluates the operation status of each of the second-tier servers based on the received operation status, which generates the status table indicating the operation status of the second-tier server, and which stores the status table in the dispatcher storage device; a table transmitter which reads the status table from the dispatcher storage device in response to the generation of the status table, and which transmits the status table to each of the first-tier servers; and a first table updating unit which updates the status table stored in the dispatcher storage device by use of the status table received in response to the reception of the status table from any of the first-tier servers; and wherein each of the first-tier servers comprises: a server storage device which stores the status table indicating the operation status of the second-tier server; a request transmitter which transmits the transaction request to the second-tier server in response to the reception of the transaction request transferred from the transferring unit of one of the dispatcher apparatuses, in order to cause the second-tier server to process a part of the transaction request; a status returning unit which returns, to the dispatcher apparatus, a status of the transaction response to the transaction request transmitted to the second-tier server, as the operation status of the second-tier server, the status of the transaction response included in the transaction response to the transaction request transferred from the transferring unit of the dispatcher apparatus; a second table updating unit which updates the status table already stored in the server storage device by use of the status table received from the table transmitter of the dispatcher apparatus, in response to the reception of the status table; and a table returning unit which returns the status table to each of the dispatcher apparatuses, in response to the update of the status table.
4. The system according to claim 1 , wherein: the table generator further evaluates the operation status of each of the first-tier servers according to a time required from transmission of the transaction request to each of the first-tier servers until reception of the transaction response to the transaction request, and generates the status table including the evaluation, and each of the dispatcher apparatuses further comprises a halt judging unit which stops the table generator receiving the operation status and the table transmitter transmitting the status table, on condition that the operation statuses of all of the first-tier servers are not in normal statuses in the status table.