As the proliferation of programming systems and data base system continues and, correspondingly, as the need for integrating these systems for certain applications increases, VM/370 offer a mechanism for such integration. This paper analyses the performance of a configuration of virtual machines using VM/370 that allows for the sharing of a data base system among several incompatible programs in an interactive environment. Specifically, two aspects of performances are addressed – an experimental study of the overhead cost incurred in the interface mechanisms employed, and a theoretical study of the degradation of response time due to the locking mechanisms employed. The conclusion of the experimental observations is that for sophisticated, complex accesses to the data base system, the overhead costs are relatively small. The result of the theoretical study is the quantification of that degradation as a function of speeds of the data base machine and the rate with which queries are made. The discussion of the practical implications of this theoretical study presents ways to improve this degradation. The observed conclusion of this work is our feeling that, for certain application areas, the benefits resulting from increased effectiveness of users outweigh the costs incurred.

This paper presents the use of the virtual machine concept as a software engineering tool. The focus is on techniques that allow the rapid integration and assimilation of existing data, models, analytical facilities, report generation facilities, and data base management systems. Since many of these models, programs, and facilities run under different operating systems, they often are incompatible with each other. By combining multiple virtual machines in a particular configuration, and allowing for communication among them, it has been possible to overcome these difficulties. The result is a set of software engineering tools that seem particularly useful in decision support systems. We present the application of these tools along with the software techniques used to implement them, and quantify some of their costs and benefits.

Traditional intuitive methods of decision-making are no longer adequate to deal with the complex problems faced by the modern policymaker. Thus systems must be developed to provide the information and analysis necessary for the decisions which must be made. These systems are called decision support systems. Although database systems provide a key ingredient to decision support systems, the problems now facing the policymaker are different from those problems to which database systems have been applied in the past. The problems are usually not known in advance, they are constantly changing, and answers are needed quickly. Hence additional technologies, methodologies, and approaches must expand the traditional areas of database and operating systems research (as well as other software and hardware research) in order for them to become truly effective in supporting policymakers. This paper describes recent work in this area and indicates where future work is needed. Specifically the paper discusses: (1) why there exists a vital need for decision support systems; (2) examples from work in the field of energy which make explicit the characteristics which distinguish these decision support systems from traditional operational and managerial systems; (3) how an awareness of decision support systems has evolved, including a brief review of work done by others and a statement of the computational needs of decision support systems which are consistent with contemporary technology; (4) an approach which has been made to meet many of these computational needs through the development and implementation of a computational facility, the Generalized Management Information System (GMIS); and (5) the application of this computational facility to a complex and important energy problem facing New England in a typical study within the New England Energy Management Information System (NEEMIS) Project.

We recognize the need to build a facility to respond to a requirement for information systems for two classes of application areas: