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

Analysis of current and future trends in synchronization, deadlock, and recovery in distributed databases

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An Integrated Distributed Storage Design Offering Data Retrievability and Recoverability Using Soft Decision Decoding of Block Codes

Active distributed storages need to assure both consistency and dynamic data support, in addition to availability, confidentiality and resiliency. Further, since storage durability suffers in untrusted and unreliable environments, it becomes crucial to (a) select the most reliable set of servers to assure data retrievability and (b) dynamically identify errant servers and restore the data to ensure data recoverability. We address the issues of concurrency, consistency, dynamic data support, data share repair, and trust management in providing persistent storage and access. The paper focuses primarily on erasure coded distributed storages (storages employing erasure coding for data dispersal). Integration of Quorum based approach using Notification propagation, with a reliability model based on server trust-reputation forms the comprehensive design proposed. Treating servers and their data shares equally at data reconstructions during data retrievals is rather inadequate in untrusted environments. The design provides a suitable platform for use of Soft Decision Decoding to overcome this inadequacy. The design has been validated by the simulation, study, and analysis carried out for Reed Solomon coded storage with varying levels of resiliency and concurrency. The proposed design can be suitably adapted in typical distributed information storages catering to global networked audience in public, untrusted, and unreliable operating environments.</p

Consistency in a Partitioned Network: A Survey

Recently, several strategies for transaction processing in partitioned distributed database systems with replicated data have been proposed. We survey these strategies in light of the competing goals of maintaining correctness and achieving high availability. Extensions and combinations are then discussed, and guidelines for the selection of a strategy for a particular application are presented

The Homeostasis Protocol: Avoiding Transaction Coordination Through Program Analysis

Datastores today rely on distribution and replication to achieve improved performance and fault-tolerance. But correctness of many applications depends on strong consistency properties - something that can impose substantial overheads, since it requires coordinating the behavior of multiple nodes. This paper describes a new approach to achieving strong consistency in distributed systems while minimizing communication between nodes. The key insight is to allow the state of the system to be inconsistent during execution, as long as this inconsistency is bounded and does not affect transaction correctness. In contrast to previous work, our approach uses program analysis to extract semantic information about permissible levels of inconsistency and is fully automated. We then employ a novel homeostasis protocol to allow sites to operate independently, without communicating, as long as any inconsistency is governed by appropriate treaties between the nodes. We discuss mechanisms for optimizing treaties based on workload characteristics to minimize communication, as well as a prototype implementation and experiments that demonstrate the benefits of our approach on common transactional benchmarks

A unified concurrency control algorithm for distributed database systems

We present a unified concurrency-control algorithm for distributed database systems in which each transaction may choose its own concurrency control protocol. Specifically, they integrate two-phase locking, timestamp ordering, and precedence agreement into one unified concurrency-control scheme. They show the correctness of the scheme and study the problem of selecting the best protocol for each transaction to optimize system performance.published_or_final_versio