Efficient commit protocols for the tree of processes model of distributed transactions

This paper describes two efficient distributed transaction commit protocols, the Presumed Abort (PA) and Presumed Commit (PC) protocols, which have been implemented in the distributed data base system R* [DSHLM82, LHMWY83]. PA and PC are extensions of the well-known two-phase (2P) commit protocol [Gray78, Lamp80, LSGGL80]. PA is optimized for read-only transactions and a class of multi-site update transactions, and PC is optimized for other classes of multi-site update transactions. The optimizations result in reduced inter-site message traffic and log writes, and, consequently, a better response time for such transactions. We derive the new protocols in a step-wise fashion by modifying the 2P protocol.