Multiversion concurrency control

About: Multiversion concurrency control is a research topic. Over the lifetime, 1605 publications have been published within this topic receiving 43880 citations. The topic is also known as: MVCC.

Making snapshot isolation serializable

Abstract: Snapshot Isolation (SI) is a multiversion concurrency control algorithm, first described in Berenson et al. [1995]. SI is attractive because it provides an isolation level that avoids many of the common concurrency anomalies, and has been implemented by Oracle and Microsoft SQL Server (with certain minor variations). SI does not guarantee serializability in all cases, but the TPC-C benchmark application [TPC-C], for example, executes under SI without serialization anomalies. All major database system products are delivered with default nonserializable isolation levels, often ones that encounter serialization anomalies more commonly than SI, and we suspect that numerous isolation errors occur each day at many large sites because of this, leading to corrupt data sometimes noted in data warehouse applications. The classical justification for lower isolation levels is that applications can be run under such levels to improve efficiency when they can be shown not to result in serious errors, but little or no guidance has been offered to application programmers and DBAs by vendors as to how to avoid such errors. This article develops a theory that characterizes when nonserializable executions of applications can occur under SI. Near the end of the article, we apply this theory to demonstrate that the TPC-C benchmark application has no serialization anomalies under SI, and then discuss how this demonstration can be generalized to other applications. We also present a discussion on how to modify the program logic of applications that are nonserializable under SI so that serializability will be guaranteed.

Hierarchical finite state machines with multiple concurrency models

Abstract: This paper studies the semantics of hierarchical finite state machines (FSM's) that are composed using various concurrency models, particularly dataflow, discrete-events, and synchronous/reactive modeling. It is argued that all three combinations are useful, and that the concurrency model can be selected independently of the decision to use hierarchical FSM's. In contrast, most formalisms that combine FSM's with concurrency models, such as statecharts (and its variants) and hybrid systems, tightly integrate the FSM semantics with the concurrency semantics. An implementation that supports three combinations is described.

Concurrency Control and Consistency of Multiple Copies of Data in Distributed Ingres

Abstract: This paper contains algorithms for ensuring the consistency of a distributed relational data base subject to multiple, concurrent updates. Also included are mechanisms to correctly update multiple copies of objects and to continue operation when less than all machines in the network are operational. Together with [4] and [12], this paper constitutes the significant portions of the design for a distributed data base version of INGRES.

Concurrency control in advanced database applications

Abstract: Concurrency control has been thoroughly studied in the context of traditional database applications such as banking and airline reservations systems. There are relatively few studies, however, that address the concurrency control issues of advanced database applications such as CAD/CAM and software development environments. The concurrency control requirements in such applications are different from those in conventional database applications; in particular, there is a need to support non-serializable cooperation among users whose transactions are long-lived and interactive, and to integrate concurrency control mechanisms with version and configuration control. This paper outlines the characteristics of data and operations in some advanced database applications, discusses their concurrency control requirements, and surveys the mechanisms proposed to address these requirements.

Commutativity-based concurrency control for abstract data types

Abstract: Two novel concurrency algorithms for abstract data types are presented that ensure serializability of transactions. It is proved that both algorithms ensure a local atomicity property called dynamic atomicity. The algorithms are quite general, permitting operations to be both partial and nondeterministic. The results returned by operations can be used in determining conflicts, thus allowing higher levels of concurrency than otherwise possible. The descriptions and proofs encompass recovery as well as concurrency control. The two algorithms use different recovery methods: one uses intentions lists, and the other uses undo logs. It is shown that conflict relations that work with one recovery method do not necessarily work with the other. A general correctness condition that must be satisfied by the combination of a recovery method and a conflict relation is identified. >