An algorithm for replication in distributed databases

International Journal of Modern Education and Computer Science, 2013

In this paper, the detailed overview of the database replication is presented. Thereafter, PDDRA (Pre-fetching based dynamic data replication algorithm) algorithm as recently published is detailed. In this algorithm, further, modifications are suggested to minimize the delay in data replication. Finally a mathematical framework is presented to evaluate mean waiting time before a data can be replicated on the requested site.

Abstract—In this paper, we are proposing a new replica control algorithm NCP (node child protocol) for the management of replicated data in distributed database system. The algorithms impose logical tree structure on a set of copies of an object. The proposed protocols reduce the quorum size of the read and write quorum. With this algorithm read operation is executed by reading one copy in a failure free environment and if the failure occur then also it read single copy .The less number data copies required for the write operation and it provide low write operation cost then the other protocols.

Proceedings 20th IEEE International Conference on Distributed Computing Systems, 2000

Replication is an area of interest to both distributed systems and databases. The solutions developed from these two perspectives are conceptually similar but differ in many aspects: model, assumptions, mechanisms, guarantees provided, and implementation. In this paper, we provide an abstract and "neutral" framework to compare replication techniques from both communities in spite of the many subtle differences. The framework has been designed to emphasize the role played by different mechanisms and to facilitate comparisons. With this, it is possible to get a functional comparison of many ideas that is valuable for both didactic and practical purposes. The paper describes the replication techniques used in both communities, compares them, and points out ways in which they can be integrated to arrive to better, more robust replication protocols.

Proceedings of the 2009 EDBT/ICDT Workshops on - EDBT/ICDT '09, 2009

In distributed systems, replication is used for ensuring availability and increasing performances. However, the heavy workload of distributed systems such as web2.0 applications or Global Distribution Systems, limits the benefit of replication if its degree (i.e., the number of replicas) is not controlled. Since every replica must perform all updates eventually, there is a point beyond which adding more replicas does not increase the throughput, because every replica is saturated by applying updates. Moreover, if the replication degree exceeds the optimal threshold, the useless replica would generate an overhead due to extra communication messages. In this paper, we propose a suitable replication management solution in order to reduce useless replicas. To this end, we define two mathematical models which approximate the appropriate number of replicas to achieve a given level of performance. Moreover, we demonstrate the feasibility of our replication management model through simulation. The results expose the effectiveness of our models and their accuracy.

1992

Abstract We present two distributed algorithms for dynamic replication of a data-item in communication networks. The algorithms are adaptive in the sense that they change the replication scheme of the item (ie the set of processors at which the data-item is replicated), as the read-write pattern of the processors in the network changes. Each algorithm continuously moves the replication scheme towards an optimal one, where optimality is defined with respect to different objective functions.

2006

ABSTRACT In this work, we address the problem of replica selection in distributed query processing over the Web, in the presence of user preferences for Quality of Service and Quality of Data. In particular, we propose RAQP, which stands for Replication-Aware Query Processing. RAQP uses an initial statically-optimized logical plan, and then selects the execution site for each operator and also selects which replica to use, thus converting the logical plan to an executable plan.

Bioscience Biotechnology Research Communications

Replication structures are research areas of all distributed databases. We provide an overview in this paper for comparing the replication strategies for such database systems. The problems considered are data consistency and scalability. These problems preserve continuity with all its replicas spread across multiple nodes between the actual real time event in the external world and the images. A framework for a replicated real time database is discussed and all time constraints are preserved. To broaden the concept of modeling a large database, a general outline is presented which aims to improve the consistency of the data.

Replication can be a success factor in database systems as well as perhaps being one of the needs of proliferation, expansion, and the rapid progress of databases and distributed technology, despite there being a strong belief among database designers that most existing solutions are not feasible due to their complexity, poor performance and lack of scalability. This paper provides an approach that can help designers in implementing eager and lazy replication mechanisms. The proposed approach contains two phases: In the first phase, the database is designed to have indicator fields that can carry the update status, and to consider the replication concepts by classifying, categorizing and determining the kinds and locations of data objects; in the second phase, the updating methodology is provided to make the implementation of eager and lazy replication mechanisms easier and reliable.

2003

We describe an operational middleware platform for maintaining the consistency of replicated data objects, called COPla (Common Object Platform). It supports both eager and lazy update propagation for replicated data in networked relational databases. The purpose of replication is to enhance the availability of data objects and services in distributed database networks. Orthogonal to recovery strategies of backed-up snapshots, logs and other measures to alleviate database downtimes, COPla caters for high availability during downtimes of parts of the network by supporting a range of different consistency modes for distributed replications of critical data objects.

2002

This paper explores the architecture, implementation and performance of a wide and local area database replication system. The architecture provides peer replication, supporting diverse application semantics, based on a group communication paradigm. Network partitions and merges, computer crashes and recoveries, and message omissions are all handled. Using a generic replication engine and the Spread group communication toolkit, we provide replication

2011

This third edition of a classic textbook can be used to teach at the senior undergraduate and graduate levels. The material concentrates on fundamental theories as well as techniques and algorithms. The advent of the Internet and the World Wide Web, and, more recently, the emergence of cloud computing and streaming data applications, has forced a renewal of interest in distributed and parallel data management, while, at the same time, requiring a rethinking of some of the traditional techniques.

Ensuring data consistency during replication is a critical research issue in a distributed system. Guaranteeing that data replicacontinues to maintain its original status and its consistency while being copied into the distributed system is still an emerging challenge. As a result of this there is an increase in risk operational disruptions in distributed databases, financial losses in database distribution, legal issues in data consistency, passivity penalties and reputational damages to the database. Maintaining the accuracy and consistency of data over its entire life-cycle is another challenge in a distributed computing environment, this prompts intruders to temper and modify data in an invisible manner without permission of its true user thereby leading to data breach and inconsistency. The new model uses Hadoop model in connection with database to create large space memory location that handles all the bulk of unstructured data in the distributed computing environment. The evaluation parameter was taken based on the efficiency of the processing speed, data consistency, memory space and data integrity. The efficiency was recorded in percentages (%).It was observed that the proposed model performed better and achieved more data consistency in the distributed database environment as the efficiency level generateda75 % accuracy.

1994

ABSTRACT Distributed database technology is expected to have a significant impact on data processing in the upcoming years. With the introduction of commercial products, expectations are that distributed database management systems will by and large replace centralized ones within the next decade. In this paper, we reflect on the promises of distributed database technology, take stock of where we are, and discuss the issues that remain to be solved.

2000

In this paper, we explore data replication protocols that provide both fault tolerance and good performance without compromising consistency. We do this by combining transactional concurrency control with group communication primitives. In our approach, transactions are executed at only one site so that not all nodes incur in the overhead of producing results. To further reduce latency, we use an optimistic multicast technique that overlaps transaction execution with total order message delivery. The protocols we present in the paper provide correct executions while minimizing overhead and providing higher scalability.

This report describes the design of a Replication Framework that facilitates the implementation and comparison of database replication techniques. Furthermore, it discusses the implementation of a Database Replication Prototype and compares the performance measurements of two replication techniques based on the Atomic Broadcast communication primitive: pessimistic active replication and optimistic active replication.