This paper presents the DHO API and its integration into a peer-to-peer Grid architecture. It provides an efficient management of critical data resources in an extensible distributed setting consisting of a set of peers that may join or leave the system. Locking and mapping of such a resource are handled transparently for users: they may access them through simple function calls. On the lowest level of the proposed architecture the Exclusive Locks for Mobile Processes ELMP algorithm ensures data consistency and guarantees the logical order of requests. All operations in our architecture have an amortized cost of O(log n). An experimental assessment validates the practicality of our proposal.