A comparative study of concurrency control algorithms for distributed databases

The declining cost of computer hardware and the increasing data processing needs of geographically dispersed organizations have led to substantial interest in distributed data management. These characteristics have led to reconsider the design of centralized databases. Distributed databases have appeared as a result of those considerations. A number of advantages result from having duplicate copies of data in a distributed databases. Some of these advantages are: increased data accesibility, more responsive data access, higher reliability, and load sharing. These and other benefits must be balanced against the additional cost and complexity introduced in doing so. This thesis considers the problem of concurrency control of multiple copy databases. Several synchronization techniques are mentioned and a few algorithms for concurrency control are evaluated and compared

Rigorous Design of Fault-Tolerant Transactions for Replicated Database Systems using Event B

System availability is improved by the replication of data objects in a distributed database system. However, during updates, the complexity of keeping replicas identical arises due to failures of sites and race conditions among conflicting transactions. Fault tolerance and reliability are key issues to be addressed in the design and architecture of these systems. Event B is a formal technique which provides a framework for developing mathematical models of distributed systems by rigorous description of the problem, gradually introducing solutions in refinement steps, and verification of solutions by discharge of proof obligations. In this paper, we present a formal development of a distributed system using Event B that ensures atomic commitment of distributed transactions consisting of communicating transaction components at participating sites. This formal approach carries the development of the system from an initial abstract specification of transactional updates on a one copy database to a detailed design containing replicated databases in refinement. Through refinement we verify that the design of the replicated database confirms to the one copy database abstraction

Survey on Secure Mining of Association Rules in Vertically Distributed Databases

A distributed database system is a collection of sites connected on a common high bandwidth network. Logically, data belongs to the same system but physically it is spread over the sites of the network, making the distribution invisible to the user. The advantage of this distribution resides in achieving availability, performance, modularity and reliability. In this paper, I have done a survey of papers related to Mining of Association Rules over distributed databases. From this survey, we have come up with a proposed solution to address the problem of secure mining of association rules where transactions are distributed in vertically distributed databases. Each site holds some attributes of each transaction and the sites wish to participate in the identification of globally valid association rules However, the sites should not reveal individual transaction data. The Protocol is based on Apriori Algorithm [2] and MultiParty Algorithm [3] for efficiently discovering frequent item sets with minimum support levels, without either site communicating individual transaction values. DOI: 10.17762/ijritcc2321-8169.15035

Performance Test Automation with Distributed Database Systems

Our previous research paper 2018;A Focus on Testing Issues in Distributed Database Systems' led us to a conclusion that Distributed Database Systems supports many good engineering practices but there is still place for refinements. A Distributed Database (DDB) is formed by a collection of multiple databases logically inter-related in a Computer Network. Apart from managing a plethora of complicated tasks, database management systems also need to be efficient in terms of concurrency, reliability, fault-tolerance and performance. As there has been a paradigm shift from centralized databases to Distributed databases, any testing process, when used in DDB correlates a series of stages for the construction of a DDB project right from the scratch and is employed in homogeneous systems. In this paper, an attempt is made to describe the establishment of Performance Testing with DDB systems. It focuses on the need for maintaining performance and some techniques to achieve performance in DDB systems. Three sample web based systems are tested by using TestMaker, one of the open source software, in order to highlight the helpful role of performance in the context of testing. The strengths and weaknesses of chosen performance testing tools viz., TestMaker, OpenSTA, and httperf are discussed

Trends in the Solution of Distributed Data Placement Problem

Data placement for optimal performance is an old problem. For example the problem dealt with the placement of relational data in distributed databases, to achieve optimal query processing time. Heterogeneous distributed systems with commodity processors evolved in response to requirement of storage and processing capacity of enormous scale. Reliability and availability are accomplished by appropriate level of data replication, and efficiency is achieved by suitable placement and processing techniques. Where to place which data, how many copies to keep, how to propagate updates so as to maximize the reliability, availability and performance are the issues addressed. In addition to processing costs, the network parameters of bandwidth limitation, speed and reliability have to be considered. This paper surveys the state of the art of published literature on these topics. We are confident that the placement problem will continue to be a research problem in the future also, with the parameters changing. Such situations will arise for example with the advance of mobile smart phones both in terms of the capability and applications

A scalable reliable instant messenger using the SD Erlang libraries

Erlang has world leading reliability capabilities, but while it scales extremely well within a single node, distributed Erlang has some scalability issues. The Scalable Distributed (SD) Erlang libraries have been designed to address the scalability limitations while preserving the reliability model, and shown to deliver significant performance benefits above 40 hosts using some relatively simple benchmarks. This paper compares the reliability and scalability of SD Erlang and distributed Erlang using an Instant Messaging (IM) server benchmark that is a far more typical Erlang application; a relatively large and sophisticated benchmark; has throughput as the key performance metric; and uses non-trivial reliability mechanisms. We provide a careful reliability evaluation using chaos monkey. The key performance results consider scenarios with and without failures on up to 17 server hosts (272 cores). We show that SD Erlang adds no performance overhead when all nodes are grouped in a single s_group. However, either adding redundant router nodes in distributed Erlang applications, or dividing a set of nodes into small s_groups in SD Erlang applications, have small negative impact. Both the distributed Erlang and SD Erlang IM tolerate failures and, up to the failure rates measured, the failures have no impact on throughput. The IM implementations show that SD Erlang preserves the distributed Erlang reliability properties and mechanisms

Referential integrity and dependencies between documents in a document oriented database

Reliability of foreign keys, which is natural in relationaldatabases, requires additional efforts when working withnon-relational databases, as non-relational database managementsystems generally don’t support foreign key constraints due totheir distributed nature. Referential integrity is an importantproperty whenever documents need to refer to each other, whichis the common case. This work discusses an implementationof a verification approach which makes use of the MapReduceprogramming model, in order to detect incorrect references indocument oriented databases that may be caused by errors inthe program code or incomplete transactions. Furthermore, themethod can be applied for the verification of more complex dependenciesbetween documents, such that bind aggregated valuesfrom certain sets of documents with the values of documentsreferred by them

Secure, reliable and dynamic access to distributed clinical data

An abundance of statistical and scientific data exists in the area of clinical and epidemiological studies. Much of this data is distributed across regional, national and international boundaries with different policies on access and usage, and a multitude of different schemata for the data often complicated by the variety of supporting clinical coding schemes. This prevents the wide scale collation and analysis of such data as is often needed to infer clinical outcomes and to determine the often moderate effect of drugs. Through grid technologies it is possible to overcome the barriers introduced by distribution of heterogeneous data and services. However reliability, dynamicity and fine-grained security are essential in this domain, and are not typically offered by current grids. The MRC funded VOTES project (Virtual Organisations for Trials and Epidemiological Studies) has implemented a prototype infrastructure specifically designed to meet these challenges. This paper describes this on-going implementation effort and the lessons learned in building grid frameworks for and within a clinical environment

A Reliable Instant Messenger in Erlang: Design and Evaluation

This document describes the design and evaluation of two Erlang-based instant messenger systems using Distributed Erlang (D-Erlang) and Scalable Distributed Erlang (SD-Erlang). The purpose of these systems is to serve as real-world benchmarks to test the performance of the SD Erlang library