TAILIEUCHUNG - Transaction Management in the R* Distributed Database Management System

Several efforts have been made since 1990 to overcome the effort required to maintain curated protein family data- bases by automatically clustering the protein sequence databases using sequence similarity. The general approach is to compute all possible pairwise comparisons, and then cluster them in some fashion, shifting the effort from humans to computers. This otherwise computationally very demanding process has benefited from the introduc- tion of the rapid PSI-BLAST system(Altschul et al., 1997). PSI-BLAST starts searching with a single sequence but then makes a multiple alignment PSSMfrom the hits after one iteration, then searches with it, and so forth. Problems with any clustering method include deciding how to delineate clusters (usually on the. | Transaction Management in the R Distributed Database Management System c. MOHAN B. LINDSAY and R. OBERMARCK IBM Almaden Research Center 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. Categories and Subject Descriptors Computer-Communication Networks Distributed Systems distributed databases Operating Systems Process Management concurrency deadlocks synchronization Operating Systems Organization and Design distributed systems Operating Systems Reliability fault tolerance Database Management General concurrency control Database Management Physical Design recovery and restart Database Management Systems distributed systems transaction processing Database Management Database Administration logging and recovery General Terms Algorithms Design Reliability Additional Key Words and Phrases Commit protocols deadlock victim selection 1. INTRODUCTION R is an experimental distributed database management system DDBMS developed and operational at the IBM San Jose Research Laboratory now renamed the IBM Almaden Research Center 18 20 . In a distributed database system the actions of a transaction an atomic unit of consistency and recovery 13 may occur at more than one site. Our model of a transaction unlike that of some other researchers 25 28 permits multiple data manipulation and definition statements to constitute a single transaction. .

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