Dynamic Replica Control Based on Fairly Assigned Variation of Data for Loosely Coupled Distributed Database Systems

This paper proposes a decentralized and asynchronous replica control method based on a fair assignment of the variation in numerical data that has weak consistency for loosely coupled database systems managed or used by different organizations of human activity. Our method eliminates the asynchronous abort of already committed transactions even if replicas in all network partitions continue to process transactions when network partitioning occurs. A decentralized and asynchronous approach is needed because it is difficult to keep a number of loosely coupled systems in working order, and replica operations performed in a centralized and synchronous way can degrade the performance of transaction processing. We eliminate the transaction abort by fairly distributing the variation in numerical data to replicas according to their demands and updating the distributed variation using only asynchronously propagated update transactions without calculating the precise global state among reachable replicas. In addition, fairly assigning the variation of data to replicas equalizes the disadvantages of processing update transactions among replicas. Fairness control for assigning the data variation is performed by averaging the variation requested by the replicas. A simulation showed that our system can achieve extremely high performance for processing update transactions and fairness among replicas. key words: data replication, weak consistency, numerical data, fairness, clock synchronization