Distributed real time database systems: background and literature review (original) (raw)

Parallel Concurrency Control Activity for Transaction Management in Real-time Database Systems

The Journal of Supercomputing, 2000

In a real-time database system, an application supports a mix of transactions. These include the real-time transactions that require completion by a given deadline. Time-critical requirements also exist in many distributed multi-media system applications. Existing concurrency control procedures introduce excessive delays due to non-availability of data resources. In this study, we ignore the delays incurred by ordinary transactions, in order to achieve a non-interference mode of execution (near parallel) for the time-critical transactions. For this purpose, a data allocation model has been studied. It is a stochastic process model based on the use of two-phase locking. It highlights the available possibilities for reductions of delays for time-critical transactions within a distributed real-time database systems. Based on the new conceptual model, modified synchronization techniques for time-critical transactions have been proposed.

A survey of Commit Protocols in Distributed Real Time database systems

— The commit processing in a Distributed Real Time Database (DRTDBS) can significantly increase execution time of a transaction. Therefore, designing a good commit protocol is important for the DRTDBS; the main challenge is the adaptation of standard commit protocol into the real time database system and so, decreasing the number of missed transaction in the systems. In these papers we review the basic commit protocols and the other protocols depend on it, for enhancing the transaction performance in DRTDBS. We propose a new commit protocol for reducing the number of transaction that missing their deadline.

Implementation of a real-time database system

Information Systems, 1996

To appear in Information Systems 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 bu er management. The system has been tested and the performance of the di erent algorithms compared in isolation as well as in combination with di erent 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.

A Protocol to Control Replication in Distributed Real-Time Database Systems

2008

Data replication is often used in distributed database systems to improve both fault tolerance and performance purposes. However, such systems must ensure replicas consistency. In this paper, we discuss the contributions of data replication in distributed real-time database systems (DRTDBS) and we then present RT-RCP, a replication control protocol we designed for DRTDBS. We introduce a new entity called List of available copies(LAC) which is a list related to each data item in the database. A LAC of a data item contains all or a part of references of its updated replicas. This allows the database to have a dynamic level of replication.

How to Manage Replicated Real-Time Databases in an Overloaded Distributed System ?

In order to meet their temporal constraints, current distributed applications such as Web-based services and electronic commerce use the technique of data replication. To take the replication benefit, we need to develop concurrency control mechanisms with high performance even when the distributed system is overloaded. In this paper, we present a protocol that uses a new notion called {\it importance value} which is associated with each real- time transaction. Under conditions of overload, this value is used to select the most important transactions with respect to the application transactions in order to pursue their execution ; the other transactions are aborted. Our protocol RCCOS (Replica Concurrency-Control for Overloaded Systems) augments the protocol MIRROR, a concurrency control protocol designed for firm-deadline applications operating on replicated real-time databases in order to manage efficiently transactions when the distributed system is overloaded. A platform is curre...

Handling Overload and Data-Relaxation Control in Distributed Real-Time Database Systems

Current applications are distributed in nature and manipulate time-critical databases with firm-deadline transactions. To guarantee performance and availability of such applications fault-tolerant mechanisms need to be developed. In the context of time critical applications, this also leads to providing means to ensure that as many as possible real-time transactions satisfy their deadline in the presence of overload. In this paper, we propose a distributed protocol, which provides mechanisms to handle overload situations while tolerating bounded data inconsistencies in the context of distributed real-time database systems.

A SURVEY ON TRANSACTIONS MANAGEMNET IN DISTRIBUTED REAL TIME DATABASE SYSTEMS

Distributed real time database systems (DRTDBS) is the collection of database which are logically correlated over heterogeneous networks and their transactions have explicit timing constraints in the form of deadlines. Managing the transaction in real time distributed database is not easy; the complexity increases in real time applications by placing deadlines on the response of database system and transaction processing. This paper presents a survey study on transactions management in DRTDBS. At the end of this paper the authors propose a model for managing a transaction in real time distributed database systems

Towards the evaluation of algorithms used in real-time databases

2005

There is a noticeable interest in merging standard database technology and real-time technology recently, resulted in combined systems known as Real-Time Database Systems. They are similar to the conventional databases, but they must ensure some degree of reliability regarding the real-time response requirements. It is very difficult to achieve guaranteed real-time database services in terms of both deadline miss ratio and data freshness because various components can compete for system resources. Transactions travel in a RTDB system through various components until their termination. Our objective is to design an experimental real-time database system which would be suitable enough to study the most important real-time database issues, including CPU scheduling, concurrency control and conflict resolution. Because of the strong interactions among the processed components, proposed system can help us to understand their effect on system performance and to identify the most important factors.

An admission control paradigm for real-time databases

1996

We propose and evaluate an admission control paradigm for RTDBS, in which a transaction is submitted to the system as a pair of processes: a primary task, and a recovery block. The execution requirements of the primary task are not known a priori, whereas those of the recovery block are known a priori. Upon the submission of a transaction, an Admission Control Mechanism is employed to decide whether to admit or reject that transaction. Once admitted, a transaction is guaranteed to finish executing before its deadline.