A Self-Adaptive Database Buffer Replacement Scheme.

The overall performance of a database system is very sensitive to the buffer replacement algorithm used. However, the performance evaluation of database buffer replacement algorithms commonly assumes that database accesses are independent and the probability for each individual database record to be accessed is fixed. Due to these rigid assumptions, the results of performance evaluation are not always reliable. In this dissertation, we apply Simon\u27s model of information accessing to model database accessing frequencies. This approach relaxes the independent assumption, and since it also allows certain dynamic behavior in accessing frequencies; thus, it is more robust and preferable over the traditional artificial data approach. Furthermore, taking advantage of the conceptual similarity between the self-organizing linear search heuristics and the traditional buffer replacement algorithms, we propose a self-adaptive buffer replacement scheme that outperforms conventional database buffer replacement algorithms. The findings of our study can be further applied to many other computer applications, e.g. the more complex problem of archival storage design in larger database systems

Performance Modelling of Database Designs using a Queueing Networks Approach. An investigation in the performance modelling and evaluation of detailed database designs using queueing network models.

Databases form the common component of many software systems, including mission critical transaction processing systems and multi-tier Internet applications. There is a large body of research in the performance of database management system components, while studies of overall database system performance have been limited. Moreover, performance models specifically targeted at the database design have not been extensively studied. This thesis attempts to address this concern by proposing a performance evaluation method for database designs based on queueing network models. The method is targeted at designs of large databases in which I/O is the dominant cost factor. The database design queueing network performance model is suitable in providing what if comparisons of database designs before database system implementation. A formal specification that captures the essential database design features while keeping the performance model sufficiently simple is presented. Furthermore, the simplicity of the modelling algorithms permits the direct mapping between database design entities and queueing network models. This affords for a more applicable performance model that provides relevant feedback to database designers and can be straightforwardly integrated into early database design development phases. The accuracy of the modelling technique is validated by modelling an open source implementation of the TPC-C benchmark. The contribution of this thesis is considered to be significant in that the majority of performance evaluation models for database systems target capacity planning or overall system properties, with limited work in detailed database transaction processing and behaviour. In addition, this work is deemed to be an improvement over previous methodologies in that the transaction is modelled at a finer granularity, and that the database design queueing network model provides for the explicit representation of active database rules and referential integrity constraints.Iqra Foundatio