Execution of replication in heterogeneous database systems

Database replication is a mechanism which allows distributed databases stay in synchronized and consistent state. In heterogeneous case there is a set of databases with different platforms, what additionally complicates this process. High demand for this technique causes that replication issue is developed very fast nowadays. Database replication mechanism consists in intercepting data modifications and propagating them to other databases where they are executed again. This process is very complex and there are many variants and types of replication. In this paper are discussed database replication classification (synchronous, asynchronous, multiple master, master slave), kinds of replication conflicts with resolving strategies, data modification capturing and publication-subscription model. There is introduced an example for realization of replication in heterogeneous environment. Also are discussed aspects of independence database assess mechanism from specific platform, what can be used in implementation of heterogeneous database replication.Предложено решение для реализации репликации в неоднородных средах баз данных при помощи моделей Master-Slave и Multiple master в синхронном и асинхронном режимах. Дана оценка возможным конфликтам и стратегии их преодоления, способам «перехвата» модификаций в базе. Рассмотрены применение схемы «публикатор–подписчик» и различные способы проведения модификаций в удаленных базах данных.Запропоновано рішення для реалізації реплікації у неоднорідних середовищах баз даних за допомогою моделей Master-Slave та Multiple master у синхронному й асинхронному режимах. Дано оцінку можливим конфліктам і стратегії їх подолання, засобам «перехоплення» модифікацій у базі. Розглянуто застосування схеми «публікатор–передплатник» і різні засоби проведення модифікацій у віддалених базах даних

Atomic Updates of Replicated Data

. Although several replication strategies have been described and compared in the literature, very few work has been published on the underlying protocols needed to support these strategies. In fact, the classical transactional protocols that are usually assumed are not fault-tolerant, and thus create a window of vulnerability for the "faulttolerant " strategies they intend to support. In this paper, we point out this issue for "quorum voting" replication strategies. We describe a faulttolerant protocol that enables to adequately support these strategies. We present some performance figures showing that, in addition to its higher resilience, our protocol provides better performance than the other possible alternatives. 1 Introduction When compared to hardware-based techniques, replication is considered as a software-based cheap way of ensuring fault-tolerance. Availability of data objects can be increased by replication. If an object is replicated on several sites, it can still be ava..