Mediation of Lazy Update Propagation in a Replicated Database over a Decentralized P2P Architecture

While replicating data over a decentralized Peer-to- Peer (P2P) network, transactions broadcasting updates arising from different peers run simultaneously so that a destination peer replica can be updated concurrently, that always causes transaction and data conflicts. Moreover, during data migration, connectivity interruption and network overload corrupt running transactions so that destination peers can experience duplicated data or improper data or missing data, hence replicas remain inconsistent. Different methodological approaches have been combined to solve these problems: the audit log technique to capture the changes made to data; the algorithmic method to design and analyse algorithms and the statistical method to analyse the performance of new algorithms and to design prediction models of the execution time based on other parameters. A Graphical User Interface software as prototype, have been designed with C #, to implement these new algorithms to obtain a database synchronizer-mediator. A stream of experiments, showed that the new algorithms were effective. So, the hypothesis according to which 201C;The execution time of replication and reconciliation transactions totally depends on independent factors.201D; has been confirmed

Bases de dados emergentes: hiper-dimensão, dados não estruturados, alta performance

Para quem precisar instalar uma solução de storage que exija elevados desempenhos, com alta disponibilidade, com capacidade em escalar e com custos aceitáveis, nunca descurando a possibilidade do suporte de dados estruturados, semi-estruturados ou não estruturados, que op ções tem? Investigaram-se os motores de bases de dados emergentes, que respondem aos desafios dos nossos tempos, e comparou-se um deles (o VoltDB) com um motor tradicional. Elaborouse um banco de testes para ambas as tecnologias em igualdade de circunstâncias, para al ém de testes específicos de escalabilidade e tolerância falhas, destinados a esta plataforma inovadora. Reunindo tecnologias já existentes por sistemas NoSql, apetrechando-as com um interface sobejamente conhecido dos programadores, o VoltDB demonstra que e poss ível fazer mais e melhor com menos recursos. Num dos testes realizados, o VoltDB realizou 225 milhões de transa ções em 22 minutos, em vez dos 10 dias, que previsivelmente um motor de bases de dados tradicional necessitaria, com o hardware utilizado; ABSTRACT: What options are available for those who need to install a data storage solution requiring high performance, high availability, capability to scale and having reasonable costs, without neglecting the possibility to support for structured, semi-structured or non-structured data? Emerging database engines that respond to the challenges of our times were analysed and one of them (VoltDB) was compared with a traditional engine. A test bench was developed for both technologies on equal terms as well as speci c tests of scalability and fault tolerance for the innovative platform. By putting together preexisting technologies in NoSQL systems and equipping them with a well known interface among programmers, the VoltDB demonstrates that it is possible to do more and better with fewer resources. In one of the tests we performed, VoltDB accomplished 225 million transactions in 22 minutes instead of the 10 days that traditional databases engine predictably would require with the hardware we used