The File Design Analyzer is a software package which evaluates well-known database storage structures and access methods in terms of secondary storage processing time and storage overhead required to service a set of user applications. It implements a first-order analytical model to specifically evaluate sequential, indexed sequential, direct access, inverted, multilist, and network storage structures. Interaction with the package is available in conversational mode, enabling the experienced analyst to conduct on-line sensitivity analysis.The paper describes three extensions of a conceptual model and system into a practical tool for evaluation of existing or proposed database designs: batched transactions, multi-access interference due to shared secondary storage, and variable record size. Case studies of real systems illustrate the potential of the File Design Analyzer to provide insight regarding the optimal choice of physical parameters within a specified storage structure and to effectively compare alternative storage structures for a particular set of applications.

Reorganization is necessary in some databases for overcoming the performance deterioration caused by updates. The paper presents a dynamic reorganization algorithm which makes the reorganization decision by measuring the database search costs. Previously, the reorganization intervals could only be determined for linear deterioration and known database lifetime. It is shown that the dynamic reorganization algorithm is near optimum for constant reorganization cost and is superior for increasing reorganization cost. In addition, it can be applied to cases of unknown database lifetime and nonlinear performance deterioration. The simplicity, generality, and efficiency appear to make this good heuristic for database reorganization.

An important problem in accessing and updating large scale data bases is the determination of when to reorganize the data and eliminate records that have been flagged for deletion but have not as yet been physically deleted. Such records take up valuable storage space and cause a degradation of access times to the active records, mainly because of the necessity to maintain overflow areas. After a certain length of time it is usually desirable to merge the old data and its overflow areas into a new data base of the original format, thus reallocating the physical storage for maximum efficiency within the constraints imposed by the data base organization. The purpose of this study is to determine the effect of various system and user parameters on the choice of optimal reorganization points over a wide range of file organizations and user applications. The analysis of file reorganization is seen as a first step toward understanding large scale data base reorganization.