PROGRESSIVE TRANSACTION RECOVERY IN DISTRIBUTED DB/DC SYSTEMS.

To perform large amounts of on-line transactions processing, several database management (DB) and data communication management (DC) subsystems can be coupled together to form a distributed DB/DC system. A key problem is to provide these distributed systems with effective means to recover transactions upon failure, while paying little performance penalty during normal processing. Also, there should be minimal interference with fault-free components during the recovery of a failed component. By decentralizing recovery management, and using transaction-level structural information to eliminate costly lower-level handshaking protocols, progressive transaction recovery protocols seek to solve the problem. A queueing model for evaluating the transaction response time during normal processing for progressive and pessimistic protocols is developed and solved, via simulation. The progressive recovery protocols are shown to reduce normal processing overhead and lead to performance improvement over the pessimistic protocol.