In this paper, we present an enhanced cacheconsistency (concurrency-control and replicamanagement) protocol and B?tree algorithms for clientserver database management systems in which the physical database is organized as a sparse (B?tree) index. We improve the concurrency-control and the callback-locking (for replica-management) protocols by augmenting these protocols with the U-locking protocol. In our cache-consistency protocol, concurrency control and replica management are performed at the page level. Our cache consistency protocol and B?tree algorithms improve concurrency in client-server database system.