In this presentation, we will describe a collection of new object-relational features that have been added to IBM's DB2 Universal Database (UDB) system. The features to be described include support for structured types, object references, and hierarchies of typed tables and views. These features will be covered from the perspective of a database designer or end user. In addition to presenting the features presently available in DB2 UDB V5.2, which became available in Fall 1998, we will discuss the expected evolution and impact of this technology over time.

A real-time database system is a database system in which transactions have explicit timing constraints such as deadlines. Apart from satisfying the database consistency constraints, transaction executions must also satisfy these timing constraints. The goal of transaction and query processing in real-time databases is to maximise the number of successful transactions in the system. This paper reports on the design, development and performance evaluation of RT-Genesis, a real-time database management system resulting from modifying an existing commercial DBMS, Genesis. RT-Genesis is a relational database management system that accommodates SQL queries and transactions having time constraints. It features time-cognizant algorithms for scheduling, concurrency control and buffer management. The system has been tested and the performance of the different algorithms compared in isolation as well as in combination with different classes of SQL workloads. In addition, a two-phased approach to transaction execution has also been implemented with the goal of exploiting access invariance to improve predictability. This work demonstrates the feasibility of converting non-real-time DBMSs into real-time DBMSs for firm deadline transactions. Besides reporting on how this was achieved and on the performance of the incorporated algorithms, lessons learned from this experience are also discussed.