Previous research on the client-server DBMS has focused on the client data caching schemes in the LAN-based client-server architectures. We investigate the issue of client data caching in the WAN environment. In the WAN environment, it is common that many clients are clustered in some local area, connected to each other over a LAN, and often request the same data to the same remote server. To take advantage of such a characteristic, we considered a client group-server DBMS architecture, in which the clients connected over a LAN in each local area form a client group and communicate with the server via a broker, a special client that belongs to the group and maintains cache consistency in its group on behalf of the server. We propose the data caching scheme called ICCC (Inter-Client Communication Caching) that fits the client group-server DBMS architecture. In ICCC, cached data can be shared among clients within the group through inter-client communication under the intervention of their broker. We conducted simulation experiments to evaluate the performance of ICCC. The results showed that ICCC considerably outperformed the standard callback locking scheme employed in the WAN environment.
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