Managing transactionswith real-time requirements presents many new problems.In this paper we address several: How can we schedule transactions with deadlines?How do the real-time constraints affect concurrency control?How should overloads be handled?How does the scheduling of 1/0 requests affect the timeliness of transactions?How should exclusive and shared locking be handled?We describe a new group of algorithms for scheduling real-time transactions that produce serializable schedules.We present a model for scheduling transactions with deadlines on a single processor disk resident database system, and evaluate the scheduling algorithms through detailed simulation experiments.

The I/O scheduling problem is examined in detail. The authors present a realistic model for studying this problem in the context of a system which executes real-time transactions. The model takes advantage of the fact that reading from the disk occurs before a transaction commits, while writing to the disk usually occurs after the transaction commits. New algorithms are presented that exploit this fact in order to meet the deadlines of individual requests. The algorithms are evaluated via detailed simulation and their performance is compared with traditional disk scheduling algorithms.>

A reliable distributed database must manage dispersed and replicated data, making them available to users in spite of hardware failures. In this paper we study the algorithms and techniques that can achieve this reliability. Three scenarios are considered for reliable (i.e., nonpartitionable) networks. In the first, data are distributed but not replicated; in the second, data are replicated; and in the third, both data and processing are fully replicated in an n-modular redundancy strategy. A brief survey of methods for handling network partitions is included.