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