Conference Paper

Revising 1-Copy Equivalence in Replicated Databases with Snapshot Isolation.

DOI: 10.1007/978-3-642-05148-7_36 Conference: On the Move to Meaningful Internet Systems: OTM 2009, Confederated International Conferences, CoopIS, DOA, IS, and ODBASE 2009, Vilamoura, Portugal, November 1-6, 2009, Proceedings, Part I
Source: DBLP


Multiple database replication protocols have used replicas supporting
the snapshot isolation level. They have provided some kind of one-copy
equivalence, but such concept was initially conceived for serializable
databases. In the snapshot isolation case, due to its reliance on
multi-versioned concurrency control that never blocks read accesses,
such one-copy equivalence admits two different variants. The first one
consists in relying on sequential replica consistency, but it does not
guarantee that the snapshot used by each transaction holds the updates
of the last committed transactions in the whole replicated system, but
only those of the last locally committed transaction. Thus, a single
user might see inconsistent results when two of her transactions have
been served by different delegate replicas: the updates of the first one
might not be in the snapshot of the second. The second variant avoids
such problem, but demands atomic replica consistency, blocking the start
(i.e., in many cases, read accesses) of new transactions. Several
protocols of each kind exist nowadays, and most of them have given
different names to their intended correctness criterion. We survey such
previous works and propose uniform names to these criteria, justifying
some of their properties.

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Available from: José Enrique Armendáriz-Iñigo, Dec 16, 2013
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    • "A family of 1SR protocols avoids the use of 2PC and relies on efficient group communication [14]. Although this leads to decreased transaction response times, it does not provide a one-copy view on the data [17] [20]. In contrast to these approaches , our SO-1SR aims at holistically optimizing the different transaction phases separately, yet not independently in order to take advantage of the scalability provided by the Cloud and its cost model (cost-awareness). "
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    ABSTRACT: Clouds are very attractive environments for deploying dif-ferent types of applications due to their pay-as-you-go cost model and their highly available and scalable infrastructure. Data management is an integral part of the applications de-ployed in the Cloud. Thus, it is of outmost importance to provide highly available and scalable data management solutions tailored to the needs of the Cloud. Data availabil-ity can be increased by using well-known replication tech-niques. Data replication also increases scalability in case of read-only transactions, but generates a considerable over-head for keeping the replicas consistent in case of update transactions. In order to meet the scalability demands of their customers, current Cloud providers use DBMSs that only support weak data consistency. While weak consis-tency is considered to be sufficient for many of the currently deployed applications in the Cloud, more and more appli-cations with strong consistency guarantees, like traditional online stores, are moved to the Cloud. In the presence of replicated data, these applications require one-copy serial-izability (1SR). Hence, in order to exploit the advantages of the Cloud also for these applications, it is essential to provide scalable, available, low-cost, and strongly consistent data management, which is able to adapt dynamically based on application and system conditions. In this paper, we present SO-1SR (self-optimizing 1SR), a novel customizable load balancing approach to transaction execution on top of replicated data in the Cloud which is able to efficiently use existing resources and to optimize transaction execution in an adaptive and dynamic manner without a dedicated load balancing component. The evaluation of SO-1SR on the ba-sis of the TPC-C benchmark in the AWS Cloud environment has shown that the SO-1SR load balancer is much more ef-ficient compared to existing load balancing techniques.
    CIKM CloudDB; 10/2013
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    • "Similar refinements to the one proposed here for 1SR can be done with other isolation levels, such as snapshot isolation [13] [14]. In this line, our group surveyed existing works and proposed uniform names for the correctness criteria of replicated databases that work with snapshot isolation [15]. The concept of serializability with external consistency, used in general distributed systems (not specifically oriented to database replication systems) and treated in different papers [16] [17], would correspond with the strictest interpretation of the database correctness criterion of 1SR. "