Adaptive multi-granularity locking protocol in object-oriented databases

Object-oriented databases can be very useful for applications containing complex data models that are not well served by conventional databases. Although much research has been done on developing concurrency control protocols for conventional databases like relational databases over the last 30 years in the concurrency control area, many of these protocols are not designed to be used in object-oriented database originally. Consequently, many opportunities presented in the rich data model of object-oriented databases are not fully utilized in the concurrency control protocols. My research presents a concurrency control protocol that will adaptively scale to the requirements of different transactions by utilizing different granularity units dynamically during each transaction. The concurrency control model proposed does not require any consistency relaxation. It uses the well-known serializability for guaranteeing consistency within the database. Concurrency control is critical as it plays a significant role in determining the performance of multi-user database systems. In this study, a self-adapting multiple granularity locking protocol is developed to improve the performance throughout and increase the degree of concurrency in object-oriented databases. This is accomplished by having a concurrency control protocol having the ability to undergo modifications in the number of locks required and the lockable granularity units according to changing transaction requirements without human input. However, it still conforms to the well-understood concept of consistency. Hence, the protocol is adaptive to the requirements of transactions. Two enhancements are proposed in this protocol. First, multiple logical granularity units are chosen with the knowledge of the data model. The protocol can freely choose the appropriate units for concurrency control. Second, escalation and de-escalation techniques are used to change the granularity units dynamically during the execution of a transaction. This is particularly important when the transaction is long lived, as is frequently the case in object-oriented databases. In this study, an adaptive multi-granularity protocol is developed and presented along with a series of simulation.