Concurrency Control in Advanced Database Applications

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

Concurrency Control in Advanced Database Applications

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

Research on fully distributed data processing systems

Issued as Quarterly progress reports, nos. 1-11, and Project report, Project no. G-36-64

A Survey of Traditional and Practical Concurrency Control in Relational Database Management Systems

Traditionally, database theory has focused on concepts such as atomicity and serializability, asserting that concurrent transaction management must enable correctness above all else. Textbooks and academic journals detail a vision of unbounded rationality, where reduced throughput because of concurrency protocols is not of tremendous concern. This thesis seeks to survey the traditional basis for concurrency in relational database management systems and contrast that with actual practice. SQL-92, the current standard for concurrency in relational database management systems has defined isolation, or allowable concurrency levels, and these are examined. Some ways in which DB2, a popular database, interprets these levels and finesses extra concurrency through performance enhancement are detailed. SQL-92 standardizes de facto relational database management systems features. Given this and a superabundance of articles in professional journals detailing steps for fine-tuning transaction concurrency, the expansion of performance tuning seems bright, even at the expense of serializabilty. Are the practical changes wrought by non-academic professionals killing traditional database concurrency ideals? Not really. Reasoned changes for performance gains advocate compromise, using complex concurrency controls when necessary for the job at hand and relaxing standards otherwise. The idea of relational database management systems is only twenty years old, and standards are still evolving. Is there still an interplay between tradition and practice? Of course. Current practice uses tradition pragmatically, not idealistically. Academic ideas help drive the systems available for use, and perhaps current practice now will help academic ideas define concurrency control concepts for relational database management systems

Theory of systems of asynchronous parallel processors

Issued as Progress report and Final report, Project no. G-36-63

Performance characteristics of semantics-based concurrency control protocols.

by Keith, Hang-kwong Mak.Thesis (M.Phil.)--Chinese University of Hong Kong, 1995.Includes bibliographical references (leaves 122-127).Abstract --- p.iAcknowledgement --- p.iiiChapter 1 --- Introduction --- p.1Chapter 2 --- Background --- p.4Chapter 2.1 --- Read/Write Model --- p.4Chapter 2.2 --- Abstract Data Type Model --- p.5Chapter 2.3 --- Overview of Semantics-Based Concurrency Control Protocols --- p.7Chapter 2.4 --- Concurrency Hierarchy --- p.9Chapter 2.5 --- Control Flow of the Strict Two Phase Locking Protocol --- p.11Chapter 2.5.1 --- Flow of an Operation --- p.12Chapter 2.5.2 --- Response Time of a Transaction --- p.13Chapter 2.5.3 --- Factors Affecting the Response Time of a Transaction --- p.14Chapter 3 --- Semantics-Based Concurrency Control Protocols --- p.16Chapter 3.1 --- Strict Two Phase Locking --- p.16Chapter 3.2 --- Conflict Relations --- p.17Chapter 3.2.1 --- Commutativity (COMM) --- p.17Chapter 3.2.2 --- Forward and Right Backward Commutativity --- p.19Chapter 3.2.3 --- Exploiting Context-Specific Information --- p.21Chapter 3.2.4 --- Relaxing Correctness Criterion by Allowing Bounded Inconsistency --- p.26Chapter 4 --- Related Work --- p.32Chapter 4.1 --- Exploiting Transaction Semantics --- p.32Chapter 4.2 --- Exploting Object Semantics --- p.34Chapter 4.3 --- Sacrificing Consistency --- p.35Chapter 4.4 --- Other Approaches --- p.37Chapter 5 --- Performance Study (Testbed Approach) --- p.39Chapter 5.1 --- System Model --- p.39Chapter 5.1.1 --- Main Memory Database --- p.39Chapter 5.1.2 --- System Configuration --- p.40Chapter 5.1.3 --- Execution of Operations --- p.41Chapter 5.1.4 --- Recovery --- p.42Chapter 5.2 --- Parameter Settings and Performance Metrics --- p.43Chapter 6 --- Performance Results and Analysis (Testbed Approach) --- p.46Chapter 6.1 --- Read/Write Model vs. Abstract Data Type Model --- p.46Chapter 6.2 --- Using Context-Specific Information --- p.52Chapter 6.3 --- Role of Conflict Ratio --- p.55Chapter 6.4 --- Relaxing the Correctness Criterion --- p.58Chapter 6.4.1 --- Overhead and Performance Gain --- p.58Chapter 6.4.2 --- Range Queries using Bounded Inconsistency --- p.63Chapter 7 --- Performance Study (Simulation Approach) --- p.69Chapter 7.1 --- Simulation Model --- p.70Chapter 7.1.1 --- Logical Queueing Model --- p.70Chapter 7.1.2 --- Physical Queueing Model --- p.71Chapter 7.2 --- Experiment Information --- p.74Chapter 7.2.1 --- Parameter Settings --- p.74Chapter 7.2.2 --- Performance Metrics --- p.75Chapter 8 --- Performance Results and Analysis (Simulation Approach) --- p.76Chapter 8.1 --- Relaxing Correctness Criterion of Serial Executions --- p.77Chapter 8.1.1 --- Impact of Resource Contention --- p.77Chapter 8.1.2 --- Impact of Infinite Resources --- p.80Chapter 8.1.3 --- Impact of Limited Resources --- p.87Chapter 8.1.4 --- Impact of Multiple Resources --- p.89Chapter 8.1.5 --- Impact of Transaction Type --- p.95Chapter 8.1.6 --- Impact of Concurrency Control Overhead --- p.96Chapter 8.2 --- Exploiting Context-Specific Information --- p.98Chapter 8.2.1 --- Impact of Limited Resource --- p.98Chapter 8.2.2 --- Impact of Infinite and Multiple Resources --- p.101Chapter 8.2.3 --- Impact of Transaction Length --- p.106Chapter 8.2.4 --- Impact of Buffer Size --- p.108Chapter 8.2.5 --- Impact of Concurrency Control Overhead --- p.110Chapter 8.3 --- Summary and Discussion --- p.113Chapter 8.3.1 --- Summary of Results --- p.113Chapter 8.3.2 --- Relaxing Correctness Criterion vs. Exploiting Context-Specific In- formation --- p.114Chapter 9 --- Conclusions --- p.116Bibliography --- p.122Chapter A --- Commutativity Tables for Queue Objects --- p.128Chapter B --- Specification of a Queue Object --- p.129Chapter C --- Commutativity Tables with Bounded Inconsistency for Queue Objects --- p.132Chapter D --- Some Implementation Issues --- p.134Chapter D.1 --- Important Data Structures --- p.134Chapter D.2 --- Conflict Checking --- p.136Chapter D.3 --- Deadlock Detection --- p.137Chapter E --- Simulation Results --- p.139Chapter E.l --- Impact of Infinite Resources (Bounded Inconsistency) --- p.140Chapter E.2 --- Impact of Multiple Resource (Bounded Inconsistency) --- p.141Chapter E.3 --- Impact of Transaction Type (Bounded Inconsistency) --- p.142Chapter E.4 --- Impact of Concurrency Control Overhead (Bounded Inconsistency) --- p.144Chapter E.4.1 --- Infinite Resources --- p.144Chapter E.4.2 --- Limited Resource --- p.146Chapter E.5 --- Impact of Resource Levels (Exploiting Context-Specific Information) --- p.149Chapter E.6 --- Impact of Buffer Size (Exploiting Context-Specific Information) --- p.150Chapter E.7 --- Impact of Concurrency Control Overhead (Exploiting Context-Specific In- formation) --- p.155Chapter E.7.1 --- Impact of Infinite Resources --- p.155Chapter E.7.2 --- Impact of Limited Resources --- p.157Chapter E.7.3 --- Impact of Transaction Length --- p.160Chapter E.7.4 --- Role of Conflict Ratio --- p.16

On computing serial dependency relations

In a database system where the data is a collection of shared objects there can be concurrent access to the data by several transactions. Traditional concurrency-controls use a notion of conflict between pairs of operations (of which the transactions are composed) to ensure correctness. Herlihy has proposed the notion of a serial dependency relation over the set of operations to capture this idea of conflict. Since the smaller the conflict relation the more the concurrency, it is of interest to construct minimal serial dependency relations. In this paper, we give necessary and sufficient conditions for a pair of operations to be related by a minimal serial dependency relation. However, we go on to show that, in general, the problem of constructing a minimal relation is undecidable. We also show that some approaches advocated for constructing serial dependency relations are not feasible in general. We then provide a sufficiency condition for cases where the minimal relations are computable

Transaction management in mobile multidatabases.

This dissertation studies transaction management in the mobile Multidatabase environment. That is, it studies the management of transactions within the context of the mobile and Multidatabase environments. Two new transaction management techniques for the mobile Multidatabase environment i.e., the PS and Semantic-PS techniques are proposed. These techniques define two now states (Disconnected and Suspended) to address the disconnectivity of the mobile user. A new Partial Global Serialization Graph algorithm is introduced to verify the isolation property of global transactions. This algorithm verifies the serializability of a global transaction by constructing a partial global serialization graph. This algorithm relies on the propagation of (serialization) information to ensure that the partial graph contains sufficient information to verify serializability of global transactions. The unfair treatment of mobile transactions due to their prolonged execution time is minimized through pre-serialization. Pre-serialization allows mobile transactions to establish their serialization order prior to completing their execution.The Internet and advances in wireless communication technology have transformed many facets of the computer environment. Virtual connectivity through the internet has lead to a new genre of software systems, i.e., cooperating autonomous systems---systems that cooperate with each other to provide extended services to the user. Multidatabase systems---a set of databases that cooperate with each other in order to provide a single logical view of the underlying information---is an example of such systems. Advances in wireless communication technology dictate that the services available to the wired user be made available to the mobile user.Finally, analytical evaluation and simulation is carried out to study the performance of these techniques and to compare their performance to that of the Kangaroo [DHB97] technique. Although the PS and Semantic-PS techniques enforce the isolation property, the evaluation results establish that the service time for these techniques in not significantly greater than that of the Kangaroo technique. In addition, the simulation establishes that pre-serialization effectively minimizes the unfair treatment of mobile transactions