Update Propagation of Replicated Data in Distributed Spatial Databases

When spatial objects are replicated at several sites in the network, the updates of a long transaction in a specific site should be propagated to the other sites for maintaining the consistency of replicated spatial objects. If any two or more transactions at different sites concurrently update some spatial objects within a given region, two spatial objects having spatial relationships should be cooperatively updated even if there are no direct conflicts of locking for them. This paper deals with the problems of replication control of spatial objects. We present the concepts of Region locking and Spatial Relationship-Bound Write locking for enhancing parallelism of updating the replicated spatial objects. If there are no spatial relationships between the two objects that are concurrently being updated at different sites, parallel updates will be completely allowed. We argue that concurrent updates of two spatial objects having spatial relationships should be propagated and cooperated by using an extended twophase commit protocol, called Spatial Relationship-based 2PC protocol.