A binary hybrid replication strategy for improving availability and maintaining consistency of data in large scale mobile environments

Data Management in mobile computing environments poses great challenges to the database researchers. One of the important challenges is to provide a data replication solution that maintains the consistency and improves the availability of replicated data. This paper addresses this problem for large scale distributed information systems that operate in mobile environments. Our solution represents a new binary hybrid replication strategy, in terms of its components and approach. The new strategy encompasses two components: replication architecture to provide a solid infrastructure for improving data availability and replication method to transfer data updates in a manner that achieves the consistency of data. The new strategy is a hybrid of both pessimistic and optimistic replication approaches, in order to exploit the features of each. The proposed strategy supports higher data availability and lower rate of inconsistencies as well as supports the mobility of users

A Comprehensive Replication Strategy for Improving Availability and Maintaining Consistency in Large-Scale Mobile Distributed Database Systems

Recent years have witnessed tremendous growth of database applications in mobile computing environments. An important challenge to database researchers in such environments is to provide a data replication solution that maintains the consistency and improves the availability of replicated data. This research addresses these problems for large scale distributed database systems that operate in mobile environments. The research called such systems as Large-Scale Mobile Distributed Database Systems (LMDDBSs). As a solution, the research provides a new comprehensive replication strategy that consists of four components in order to act in accord with the characteristics of LMDDBSs, and to better support the mobility and disconnections of mobile hosts. The components of the replication strategy are: replication architecture, updates propagation protocol, updates ordering mechanism, and replication method. The effectiveness of the proposed strategy with respect to updates propagation is verified through a comparative study with Roam replication system. The results revealed that the proposed strategy achieves better propagation delay and lesser total number of messages than Roam. Moreover, the proposed strategy achieves load balance in both propagation and ordering processes. Also, the proposed updates propagation protocol is compared with N-ary tree based propagation protocol. The results showed that the horizontal extension provided by the proposed protocol is more suitable than the vertical extension for LMDDBSs. The characteristic of updates ordering mechanism reveals that it is more suitable to meet the ordering requirements of LMDDBSs than the previous mechanisms that are based on version vectors. To analyze the stochastic behavior of the replication system, the research developed a Stochastic Petri Net (SPN) model. The analysis proved that the mobile database state in which availability and consistency are satisfied is a recurrent state with a probability that depends on the number of the synchronizations of the mobile host with the fixed network. Keywords: availability, consistency, optimistic replication, pessimistic replication, replication method, propagation protocol

Exploiting Cloud Computing and Web Services to Achieve Data Consistency, Availability, and Partition Tolerance in the Large-Scale Pervasive Systems

This article presents a new comprehensive approach to realize a sufficient trade-off between the CAP properties (i.e., consistency, availability, and partition tolerance) in the large-scale pervasive information systems. To achieve these critical properties, the capabilities of both cloud computing and web services were exploited in developing the components of the proposed approach. These components include a cloud-based replication architecture for ensuring high data availability and achieving partition tolerance, a web services-based middleware for maintaining the eventual consistency, and a data caching scheme to enable the mobile computing elements to conduct  update transactions during the disconnection periods.  The evaluation of the performance aspects revealed that the proposed approach is able to achieve a load balance, lower propagation delay, and higher cache hit ratio, as compared to other baseline approaches