C.-H. Chang

Bio: C.-H. Chang is an academic researcher from Konkuk University. The author has contributed to research in topics: Stateless protocol & Two-phase commit protocol. The author has an hindex of 1, co-authored 1 publications receiving 213 citations.

A real-time locking protocol

Abstract: The authors examine a priority driven two-phase lock protocol called the read/write priority ceiling protocol. It is shown that this protocol leads to freedom from mutual deadlock. In addition, a high-priority transactions can be blocked by lower priority transactions for at most the duration of a single embedded transaction. These properties can be used by schedulability analysis to guarantee that a set of periodic transactions using this protocol can always meet its deadlines. Finally, the performance of this protocol is examined for randomly arriving transactions using simulation studies. >

Real Time Scheduling Theory: A Historical Perspective

Abstract: In this 25th year anniversary paper for the IEEE Real Time Systems Symposium, we review the key results in real-time scheduling theory and the historical events that led to the establishment of the current real-time computing infrastructure. We conclude this paper by looking at the challenges ahead of us.

Temporal and real-time databases: a survey

Abstract: A temporal database contains time-varying data. In a real-time database transactions have deadlines or timing constraints. In this paper we review the substantial research in these two previously separate areas. First we characterize the time domain; then we investigate temporal and real-time data models. We evaluate temporal and real-time query languages along several dimensions. We examine temporal and real-time DBMS implementation. Finally, we summarize major research accomplishments to date and list several unanswered research questions. >

On real-time databases: concurrency control and scheduling

Abstract: In addition to maintaining database consistency as in conventional databases, real-time database systems must also handle transactions with timing constraints. While transaction response time and throughput are usually used to measure a conventional database system, the percentage of transactions satisfying the deadlines or a time-critical value function is often used to evaluate a real-time database system. Scheduling real-time transactions is far more complex than traditional real-time scheduling in the sense that (1) worst case execution times are typically hard to estimate, since not only CPU but also I/O requirement is involved; and (2) certain aspects of concurrency control may not integrate well with real-time scheduling. In this paper, we first develop a taxonomy of the underlying design space of concurrency control including the various techniques for achieving serializability and improving performance. This taxonomy provides us with a foundation for addressing the real-time issues. We then consider the integration of concurrency control with real-time requirements. The implications of using run policies to better utilize real-time scheduling in a database environment are examined. Finally, as timing constraints may be more important than data consistency in certain hard realtime database applications, we also discuss several approaches that explore the nonserializable semantics of real-time transactions to meet the hard deadlines. >

Concurrency control in real-time databases by dynamic adjustment of serialization order

Abstract: A new concurrency control algorithm for real-time database systems is proposed, by which real-time scheduling and concurrency control can be integrated. The algorithm is founded on a priority-based locking mechanism to support time-critical scheduling by adjusting the serialization order dynamically in favor of high priority transactions. Furthermore, it does not assume any knowledge about the data requirements or execution time of each transaction, making the algorithm very practical. >

An overview of real-time database systems

Abstract: Traditionally, real-time systems manage their data (e.g. chamber temperature, aircraft locations) in application dependent structures. As real-time systems evolve, their applications become more complex and require access to more data. It thus becomes necessary to manage the data in a systematic and organized fashion. Database management systems provide tools for such organization, so in recent years there has been interest in “merging” database and real-time technology. The resulting integrated system, which provides database operations with real-time constraints is generally called a real-time database system (RTDBS) [1].