Data Placement, Logging and Recovery in Real-Time Active Databases

Abstract

In the past, real-time transaction processing systems have largely considered transaction characteristics such as deadlines and criticality when scheduling or aborting transactions, and when performing concurrency control and buffer management. Active database researchers have been involved in the development of system models that incorporate the Event- Condition-Action paradigm. They have examined issues related to the specification and recognition of different types of events and conditions and the relationships of triggering and triggered actions. With the growing need to provide for both active and real-time capabilities, novel techniques, combining the two areas must be developed. Existing techniques have several deficiencies. Data characteristics have not been explicitly considered to do transaction processing. The impact of data characteristics on data placement, logging and recovery issues have not been studied. We show that exploiting the characteristics of data for transaction processing, placing the data at the appropriate level of the memory hierarchy, and performing logging and recovery of data appropriate for each type of data is crucial to achieve high performance in real-time active database systems.