This paper deals with the transaction management aspects of the R* distributed database system. It concentrates primarily on the description of the R* commit protocols, Presumed Abort (PA) and Presumed Commit (PC). PA and PC are extensions of the well-known, two-phase (2P) commit protocol. PA is optimized for read-only transactions and a class of multisite update transactions, and PC is optimized for other classes of multisite update transactions. The optimizations result in reduced intersite message traffic and log writes, and, consequently, a better response time. The paper also discusses R*'s approach toward distributed deadlock detection and resolution.
We propose an algorithm for detecting deadlocks among transactions running concurrently in a distributed processing network (i.e., a distributed database system). The proposed algorithm is a distributed deadlock detection algorithm. A proof of the correctness of the distributed portion of the algorithm is given, followed by an example of the algorithm in operation. The performance characteristics of the algorithm are also presented.
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