Multi-level concurrency control of a database system

A typical database system maintains target data, which contain information useful for users, and access path data, which facilitate faster accesses to target data. Further, most large database systems support concurrent processing of multiple transactions. For a static database system model, where units of concurrency control are not dynamically created or deleted, various concurrency control methods are known. Also, many methods that allow concurrent accesses to indexing structures without invalidating their integrity are known. However, a straightforward integration of these two kinds of concurrency control methods fails because of the phantom problem. In this paper, we introduce group locks in order to solve this problem and discuss their implementation. As one side benefit of introducing group locks, we show that if the lowest-level access path data as well as the target data are two-phase locked by transactions, consistency of the logical data will be preserved

Economic data bank management in a developing nation

This dissertation describes the results of a research project which was undertaken at Loughborough University of Technology. The basic objectives of the research project were: (1) to investigate the management elements required for organising the development of an Economic Data Bank (EDB), with particular emphasis on the requirements of a developing nation; (2) to investigate the sociological, political and technical implications associated with organising the development of an EDB in a developing nation. A theoretical framework was established for this study. This was dene after an extensive search and review of literature was performed in the areas of data and data base management systems, management information systems, and computer technology in general. [Continues.

An error recovery scheme for concurrent processes

PhD ThesisWith the more widespread use of multi- processors and distributed computing systems, programmers need a simple, reliable interface to them. This thesis describes language constructs, and mechanisms for their support, that can be used in the implementation of fault-tolerant concurrent processes. The basic language structure is the Atomic Action, supported by a modified recovery cache mechanism. This combines the collection of recovery data with the locking of resources and allows recovery blocks to be integrated with Atomic Actions. Synchronisation between actions is discussed, as well as a means of detecting and breaking deadlocks, based on the use of a "blocking graph". Reliable communication and cooperation between actions is considered, and several constructs are investigated. The limitations of Shared Atomic Actions are identified, and, further, the use of a form of reliable "secretary" is shown to lead to unnecessary recovery activity. These problems are resolved by structures based on a classification of resources by the way they are used in programs. Also contained in the thesis are descriptions of trial implementations of some of the mechanisms described, and a discussion of existing concurrent programming techniques.Science Research Council of Great Britai