A method for managing a remote backup database to provide protection from disasters that destroy the primary database is presented. The method is general enough to accommodate the ARIES-type recovery and concurrency control methods as well as the methods used by other systems such as DB2, DL/I and IMS Fast Path. It provides high performance by exploiting parallelism and by reducing inputs and outputs using different means, like log analysis and choosing a different buffer management policy from the primary one. Techniques are proposed for checkpointing the state of the backup system so that recovery can be performed quickly in case the backup system fails, and for allowing new transaction activity to begin even as the backup is taking over a primary failure. Some performance measurements taken from a prototype are also presented.>

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.