Browsing by Author "Haritsa, Jayant R."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item Data Access Scheduling in Firm Real-Time Database Systems(1992) Haritsa, Jayant R.; Carey, Micheal J.; Livny, Miron; ISRA major challenge addressed by conventional database systems has been to efficiently implement the transaction model, which provides the properties of atomicity, serializability, and permanence. Real-time applications have added a complex new dimension to this challenge by placing deadlines on the response time of the database system. In this paper, we examine the problem of real-time data access scheduling, that is, the problem of scheduling the data accesses of real-time transactions in order to meet their deadlines. In particular, we focus on "firm deadline" real-time database applications, where transactions that miss their deadlines are discarded and the objective of the real-time database system is to minimize the number of missed deadlines. Within this framework, we use a detailed simulation model to compare the performance of several real-time locking protocols and optimistic concurrency control algorithms under a variety of real-time transaction workloads. The results of our study show that in moving from the conventional database system domain to the real-time domain, there are new performance-related forces that come into effect. Our experiments demonstrate that these factors can cause performance recommendations that were valid in a conventional database setting to be significantly altered in the corresponding real-time setting.Item Design of the MANDATE MIB(1993) Haritsa, Jayant R.; Ball, Michael O.; Roussopoulos, Nicholas; Baras, John S.; Datta, Anindya; ISR; CSHCNA management information database is the heart of a network management system -- it provides the interface between all functions of the network management system, and therefore has to provide sophisticated functionality allied with high performance. In this paper, we introduce the design of MANDATE, a database system that is designed to effectively support the management of large enterprise network. MANDATE proposes to use special characteristics of network management data and transactions, together with recent advances in database technology, to efficiently derive its functionality.Item ICON: A System for Implementing Constraints in Object-based Networks(1994) Goli, Shravan K.; Haritsa, Jayant R.; Roussopoulos, N.; ISR; CSHCNIn today's Network Management scenario, the network operator's interface to the network is through a Management Information Base (MIB). The MIB stores all management related data such as configuration information, performance statistics, and trouble logs and so on. Configuration management, which is at the core of network management, is implemented through the MIB in a three step process: making updates to MIB data elements, checking the validity of the updates, propagating the effects of the updates to the network elements. While all three steps need to be executed efficiently for the MIB to serve its intended goal, the second step of checking update validity is especially important from the management viewpoint. For example, if an operator mistakenly configures a ninth port on an eight port card, it is essential that the MIB should both detect and prevent this error. Allowing such operations to go through would have adverse impact on the performance of the network (since it increases the network management traffic). Therefore, we focus primarily on the problem of checking the validity of updates to MIB data elements, which can be viewed as a specific instance of the general problem of constraint management in database systems. We introduce the design of ICON (Implementing Constraints in Object-based Networks), a proposed constraint management system. In ICON, constrains are expressed through rules. Each rule is composed of an event, a condition, and an action. Occurrence of the event triggers the rule, the condition is a boolean check, and the action is executed if the condition is satisfied. Rules and events are also treated as objects so that they can be created, modified, and deleted like other objects, thus providing a uniform view of rules and events in an OO context. The OO paradigm results in an extensible and a reusable system. To our knowledge, not much work has been done in this area and this paper would trigger further research in this area.Item MANDATE: MAnaging Networks using DAtabase TEchnology(1992) Haritsa, Jayant R.; Ball, Michael O.; Roussopoulos, N.; Datta, Anindya; ISRIn a recent opinion poll of telecommunications executives, enterprise network management was identified to be the top technological issue of the future. At present, however, there do not exist any viable solutions to this critical problem. Therefore, considerable research efforts are being focused on the development of effective network management tools. A management information database is the heart of a network management system - it provides the interface between all functions of the network management system, and therefore has to provide sophisticated functionality allied with high performance. In this paper, we describe MANDATE (MAnaging Networks using DAtabase TEchnology), a database system that is designed to effectively support the management of large networks of the future. MANDATE uses special characteristics of network management data and transactions, together with recent advances in database technology, to efficiently derive its functionality.Item Performance Analysis of Real-Time Database Systems(1992) Haritsa, Jayant R.; ISRDuring the past few years, several studies have been made on the performance of real-time database systems with respect to the number of transactions that miss their deadlines. All of these studies have used simulation models or database testbeds as their performance evaluation tools. We present, in this paper, a preliminary analytical performance study of real-time transaction processing. Using a series of approximations, we derive simple closed-form solutions to reduced real-time database models. By virtue of their simplicity, these solutions provide considerable insight into the observed performance. Although quantitatively approximate, the solutions accurately capture system sensitivity to workload parameters and yield performance bounds. Our results indicate that increased transaction slack times degrade performance under heavy loads for the real-time database systems considered in this study. The analysis also shows that the absolute sizes of transaction data sets, independent of their relationship to the database size, have a significant impact on performance. Interestingly, our approximation techniques for real-time database models are applicable to classical single- server real-time models as well, resulting in simple approximations that closely match complex exact solutions presented in the literature.Item ROBUST: A Hardware Solution to Real-Time Overload(1992) Baruah, Sanjoy; Haritsa, Jayant R.; ISRIt has been proven that no on-line scheduling algorithm can guarantee a processor utilization greater than 25% under conditions of overload. From this result, it follows that there is no satisfactory software solution (within the paradigm of deterministic computation) to the problem of constructing overload-tolerant real-time systems, and we are forced to consider alternative remedies. In this paper, we describe an attempt at a hardware solution. In particular, we quantify the advantages of using faster hardware in real-time systems. An obvious advantage is that more work can be done in a shorter amount of time and the system is therefore less likely to enter overload. More interestingly, we prove that the performance of systems using faster hardware improves dramatically over systems using slower hardware if overload does occur. We present here a new scheduler, ROBUST, which efficiently uses faster hardware to prevent performance degradation under overload conditions.