Performance evaluation of concurrency control techniques for database management systems

A database is a symbolic representation of the state of a part of the real world in terms of computable objects. The state of the part of the real world is not static and every change in this state must be reflected in the database.Integrity of the database is defined as the maintainence of the attributes of the computable objects or entities. Semantics of these entities are well-defined by the database designer; the entities change their values under semantic constraints or semantic integrity assertions. A database state is a mapping from name to value and Transactions are mechanisms which change database state. In order to improve system response and to achieve optimum resource utilization transactions are scheduled concurrently. However, this way of scheduling transactions can have an adverse effect on the integrity of the database if it is not managed properly. The mechanisms which control the concurrent scheduling of transactions are called Synchronization or Concurrency Control Techniques. There are several types of these, each with its advantages and disadvantages. In this work an extensive performance study of these techniques, using simulation models, has been done and an attempt made to define relationships between the environment and the type of synchronization technique.