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

Performance measurement and analysis of large filestores

PhD ThesisPerformance measurements of two large time-sharing computer systems are presented, with emphasis on their disk filestores. Similarities of process behaviour are found in the measured systems and another system reported in the literature. Individual processes make i/o requests in sequences, or bursts. Burst lengths have a mean of two with a large variance; within a burst, file i/o requests are spatially sequential in intent and are temporally related. Characterizations of these behaviour patterns form the basis of a methodology for filestore evaluation and design. Descriptions of spatial and temporal load are abstracted from software traces without loss of any performance factor; these descriptions are inputs to a statistical model of the processes in the environment of the filestore. The filestore is represented by a simulation queuing model. The method specifies the inputs to the composite model and describes the calibration of outputs to match observable outputs. A model is built by this method, and validated for different loads. The model is used for three evaluation experiments. Disk request scheduling is not statistically significant; filestore layout and disk capacity are highly significant; disks with fast-access areas are shown to improve performance by taking advantage of spatial accessing patterns. The limits of performance of a novel filestore equipped with a cache store are explored to determine guidelines for this new design. Modest improvements resulting from this design are shown to produce a considerable improvement in overall system performance.The Science Research Council: The University of Newcastle upon Tyne

Modeling of Physical Database Design and Performance Analysis With Emphasis on VSAM Files.

Growth in the size of a database is reflected in deterioration of database performance. Since deterioration is related to the structure of the file, the performance efficiency involves the design of a physical database and the proper management of it. This research addresses a modeling procedure of a physical database design considering both records insertions and deletions. The model describes the behavior of a physical database in a VSAM file environment, and is extended to the issue of database reorganization through a cost analysis. The cost of accessing the database increases due to the physical disorganization of the database caused by records updates and insertions. A cost function that describes this excess cost is defined. As a remedy of the performance deterioration, database reorganization is required. Optimum reorganization points are obtained as a tradeoff between the excessive costs and the reorganization cost. Numerical examples based on the characteristics of IBM 3380 are given

NASA RECON: Course Development, Administration, and Evaluation

The R and D activities addressing the development, administration, and evaluation of a set of transportable, college-level courses to educate science and engineering students in the effective use of automated scientific and technical information storage and retrieval systems, and, in particular, in the use of the NASA RECON system, are discussed. The long-range scope and objectives of these contracted activities are overviewed and the progress which has been made toward these objectives during FY 1983-1984 is highlighted. In addition, the results of a survey of 237 colleges and universities addressing course needs are presented