Network database evaluation using analytical modeling

The proliferation of computerized databases and the widespread demand for timely access to data has resulted in the need to develop automated techniques for database design. In the past, database design was accomplished manually by data processing personnel through past experience and trial and error. However, the implementation of large integrated databases in organizations made it increasingly difficult for individual users to do the necessary design. A new approach was required to consider the many tradeoffs among user objectives and within the complex logical structures required to integrate the various types of data. The stages of database design have only recently been well-defined, 5 and much of that work is still done manually with some assorted design aids available at some of the stages. One of the more quantifiable stages in the database design process is the implementation of a physical database from a logical database design. Logical database design results in the definition of record types and their relationships under the constraints of a particular data model, but independent of physical structure. The design of the physical database must take into account the variations in access methods, i.e., the access paths and search mechanisms available, as well as physical clustering of records near each other within blocks or in a contiguously defined set of blocks. Considerably more insight is required in physical database design before determining whether or not it can be accomplished independently of logical database design. Currently there exist some very general physical database designers10,13 which address tradeoffs among major classes of storage structure. On the other hand, several evaluators of physical databases have also been proposed. Some are simulation models and are quite expensive to run. 2,7,9 Others are probabilistic and are limited by expected value assumptions. 3,11 This paper described the concepts leading to the development of an operational Database Design Evaluator (DBDE), which accounts for the more significant parameters affecting physical database design performance and yet is computationally fast enough for consideration as the central module of a physical designer. The DBDE is a software