A note on the performance analysis of static locking in distributed database systems

Even though transaction deadlocks can severely affect the performance of distributed database systems, many current evaluation techniques ignore this aspect. Shyu and Li proposed an evaluation method which takes deadlocks into consideration. However, their technique is limited to exclusive locking. Using this technique, researchers illustrate the impact of deadlocks in the presence of shared locking on distributed database performance

Lock-based Protocols for Cooperation on XML Documents

The eXtensible Markup Language (XML) is well accepted in several different Web application areas. As soon as many users and applications work concurrently on the same collection of XML documents - e.g. on an XML database via a Web interface - isolating accesses and modifications of different transactions becomes an important issue. We discuss four different core protocols for synchronizing access to and modifications of XML document collections. These core protocols synchronize structure traversals and modifications. They are meant to be integrated into a native XML base management System (XBMS) and are based on two phase locking. We also demonstrate the different degrees of cooperation that are possible with these protocols by various experimental results. Furthermore, we also discuss extensions of these core protocols to full-fledged protocols. Further, we show how to achieve a higher degree of concurrency by exploiting the semantics expressed in Document Type Definitions (DTDs)

Self-adjusting multi-granularity locking protocol for object-oriented databases

Object-oriented databases have the potential to be used for data-intensive, multi-user applications that are not well served by traditional applications. Despite the fact that there has been extensive research done for relational databases in the area of concurrency control; many of the approaches are not suitable for the complex data model of object-oriented databases. This thesis presents a self-adjusting multi-granularity locking protocol (SAML) which facilitates choosing an appropriate locking granule according to the requirements of the transactions and encompasses less overhead and provides better concurrency compared to some of the existing protocols. Though there has been another adaptive multi-granularity protocol called AMGL [1] which provides the same degree of concurrency as SAML: SAML has been proven to have significantly reduced the number of locks and hence the locking overhead compared to AMGL. Experimental results show that SAML performs the best when the workload is high in the system and transactions are long-lived

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

Isolation in XML Bases

The eXtensible Markup Language (XML) is well accepted in many different application areas. As a consequence, there is an increasing need for persistently storing XML documents. As soon as many users and applications work concurrently on the same collection of XML documents - i.e. an XML base - isolating accesses and modifications of different transactions becomes an important issue. We discuss six different core protocols for synchronizing access to and modifications of XML document collections. These core protocols synchronize structure traversals and modifications. They are meant to be integrated into a native XML base management System (XBMS). Four of the six core protocols are based on two phase locking, one uses time stamps, and the last one uses a novel dynamic commit-ordering approach. The latter two protocols achieve a higher degree of concurrency by a novel implicit representation of multiple versions. We also discuss extensions of these core protocols to full-fledged protocols. Further, we show how the two phase locking based protocols can achieve a higher degree of concurrency by exploiting the semantics expressed in Document Type Definitions (DTDs)

Analysis of concurrency control protocols for real-time database systems

Cataloged from PDF version of article.This paper provides an approximate analytic solution method for evaluating the performance of concurrency control protocols developed for real-time database systems (RTDBSs). Transactions processed in a RTDBS are associated with timing constraints typically in the form of deadlines. The primary consideration in developing a RTDBS concurrency control protocol is the fact that satisfaction of the timing constraints of transactions is as important as maintaining the consistency of the underlying database. The proposed solution method provides the evaluation of the performance of concurrency control protocols in terms of the satisfaction rate of timing constraints. As a case study, a RTDBS concurrency control protocol, called High Priority, is analyzed using the proposed method. The accuracy of the performance results obtained is ascertained via simulation. The solution method is also used to investigate the real-time performance benefits of the High Priority over the ordinary Two-Phase Locking. © 1998 Elsevier Science Inc. All rights reserved

Performance models of concurrency control protocols for transaction processing systems

Transaction processing plays a key role in a lot of IT infrastructures. It is widely used in a variety of contexts, spanning from database management systems to concurrent programming tools. Transaction processing systems leverage on concurrency control protocols, which allow them to concurrently process transactions preserving essential properties, as isolation and atomicity. Performance is a critical aspect of transaction processing systems, and it is unavoidably affected by the concurrency control. For this reason, methods and techniques to assess and predict the performance of concurrency control protocols are of interest for many IT players, including application designers, developers and system administrators. The analysis and the proper understanding of the impact on the system performance of these protocols require quantitative approaches. Analytical modeling is a practical approach for building cost-effective computer system performance models, enabling us to quantitatively describe the complex dynamics characterizing these systems. In this dissertation we present analytical performance models of concurrency control protocols. We deal with both traditional transaction processing systems, such as database management systems, and emerging ones, as transactional memories. The analysis focuses on widely used protocols, providing detailed performance models and validation studies. In addition, we propose new modeling approaches, which also broaden the scope of our study towards a more realistic, application-oriented, performance analysis