Abstract: Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traflc gives a thousand fold increase in deadlocks or reconciliations. Master copy replica-tion (primary copyj schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update trans-actions that are later applied to a master copy. Commutative update transactions avoid the instability of other replication schemes. 1.

A read-only transaction or query is a transaction which does not modify any data. Read-only transactions could be processed with general transaction processing algorithms, but in many cases it is more efficient to process read-only transactions with special algorithms which take advantage of the knowledge that the transaction only reads. This paper defines the various consistency and currency requirements that read-only transactions may have. The processing of the different classes of read-only transactions in a distributed database is discussed. The concept of R insularity is introduced to characterize both the read-only and update algorithms. Several simple update and read-only transaction processing algorithms are presented to illustrate how the query requirements and the update algorithms affect the read-only transaction processing algorithms.

ing with credit is permitted. To copy otherwise, to republish, to post on servers, or to redistribute to lists, requires prior specific permission and/or a fee. Request permissions from Publications Dept, ACM Inc., fax +1 (212) 869-0481, or permissions@acm.org. 174 The Dangers of Replication and a Solution Jim Gray (Gray@Microsoft.com) Pat Helland (PHelland@Microsoft.com) Patrick O'Neil (POneil@cs.UMB.edu) Dennis Shasha (Shasha@cs.NYU.edu) Abstract: Update anywhere-anytime-anyway transactional replication has unstable behavior as the workload scales up: a ten-fold increase in nodes and traffic gives a thousand fold increase in deadlocks or reconciliations. Master copy replication (primary copy) schemes reduce this problem. A simple analytic model demonstrates these results. A new two-tier replication algorithm is proposed that allows mobile (disconnected) applications to propose tentative update transactions that are later applied to a master copy. Commutative update transacti...

The increasing demand for high throughputs in transaction processing systems leads to high degrees of transaction concurrency and hence high data contention. The conventional dynamic two-phase locking (2PL) concurrency control (CC) technique causes system thrashing at high data contention levels, restricting transaction throughput. Optimistic concurrency control (OCC) is an alternative strategy, but OCC techniques suffer from wasted resources caused by repeated transaction restarts. We propose a new technique, ORDER, that enlists the aid of the interconnection network in a distributed database system in order to coordinate transactions. The network in an ORDER system provides total ordering of messages at a low cost, enabling efficient CC. We compare the performance of dynamic 2PL and ORDER, using both an analytical model and a simulation. Unlike previously-proposed models for 2PL, our analytical model predicts performance accurately even under high data contention. We study the effects of various parameters on performance, and demonstrate that ORDER outperforms dynamic 2PL for a wide range of workloads.