The use of parallel database systems to deliver high performance has become quite common. Although queries submitted to these database systems are executed in parallel, the interaction between applications and current parallel database systems is serial. As the complexity of the applications and the amount of data they access increases, the need to parallelize applications also increases. In this parallel application environment, a serial interface to the database could become the bottleneck in the performance of the application. Hence, parallel database systems should support interfaces that allow the applications to interact with the database system in parallel. We present a taxonomy of such parallel interfaces, namely the Single Coordinator, Multiple Coordinator, Hybrid Parallel, and Pure Parallel interfaces. Furthermore, we discuss how each of these interfaces can be realized and in the process introduce new constructs that enable the implementation of the interfaces. We also qualitatively evaluate each of the interfaces with respect to their restrictiveness and performance impact.

Client-server systems cache data in client buffers to deliver good performance. Several efficient protocols have been proposed to maintain the coherence of the cached data. However, none of the protocols distinguish between index pages and data pages. We propose a new coherence protocol, called relaxed index consistency, that exploits the inherent differences in the coherence and concurrency control (C&CC) requirements for index and data pages. The key idea is to incur a small increase in computation time at the clients to gain a significant reduction in the number of messages exchanged between the clients and the servers. The protocol uses concurrency control on data pages to maintain the coherence of index pages. A performance-conscious implementation of the protocol that makes judicious use of version numbers is proposed. We show, through both qualitative and quantitative analyses, the performance benefits of making the distinction between index pages and data pages for the purposes of C&CC. Our simulation studies show that the relaxed index consistency protocol improves system throughput by as much as 15% to 88%, based on the workload.

Once considered a novelty, object oriented systems have now entered the mainstream. Their impressive performance and rich type systems have created a demand for object oriented features in other areas, such as relational database systems. We believe the current efforts to combine object oriented and relational features into a single hybrid system will fall short of the mark, whereas our approach, the co-existence approach, has the distinction of requiring far less work, but at the same time promising both the desired functionality and performance. We describe the attributes of our co-existing systems, an object oriented system (C++) and a relational system (Starburst), and show how this combination supports the desired features of both object-oriented and relational systems.