Database replication is a way to increase system performance and fault-tolerance of a given system. The price to pay is the effort needed to guarantee data consistency, and this is not an easy task. In this paper, we introduce a description of two 1-Copy-Serializable (1CS)  eager update everywhere replication protocols. The preliminary results of their… (More)
Several previous works have proven that there is no way of guaranteeing a snapshot isolation level in symmetrical repli-cated database systems without blocking transactions when they are started. As a result of this, the generalized snapshot isolation (GSI) level was defined, relaxing a bit the freshness of the snapshot being taken when a transaction is… (More)
Middleware database replication is a way to increase availability and afford site failures for dynamic content websites. There are several replication protocols that ensure data consistency for these systems. The most attractive ones are those providing Generalized Snapshot Isolation (GSI), as read operations never block. These replication protocols are… (More)
In this work, we present the correctness criteria that ensures a replicated database behaves like a single copy where trans-actions see a weaker form of SI, called Generalized-SI, with deferred update protocols in a crash failure scenario.
Database replication protocols based on a certification approach are usually the best ones for achieving good performance. The weak voting approach achieves a slightly longer transaction completion time, but with a lower abortion rate. So, both techniques can be considered as the best ones for replication when performance is a must, and both of them take… (More)
We describe a recovery protocol which boosts availability, fault tolerance and performance by enabling failed network nodes to resume an active role immediately after they start recovering. The protocol is designed to work in tandem with middleware-based eager update-everywhere strategies and related group communication systems. The latter provide view… (More)
Data replication techniques are widely used for improving availability in software applications. Replicated systems have traditionally assumed the fail-stop model, which limits fault tolerance. For this reason, there is a strong motivation to adopt the crash-recovery model, in which replicas can dynamically leave and join the system. With the aim to point… (More)
In database replication, primary-copy systems sort out easily the problem of keeping replicate data consistent by allowing only updates at the primary copy. While this kind of systems are very efficient with workloads dominated by read-only transactions, the update-everywhere approach is more suitable for heavy update loads. However, it behaves worse when… (More)