Oct. 8, 2012
-- Synchronous replication provides real-time replication and similar devices and system-based replication equipment such as geo-mirror. If synchronous writes occur in the replication environment, Oracle provides a local copy of the duplicate copies of all written table and well written. Write not in the order of deferred down before. Instead it is implemented immediately.
Synchronous replication seems ideal for high availability. However, practical constraints make it very difficult to do. For example, a network connection requires extremely strong (especially during peak hours). Reduced network bandwidth or resource performance beyond terrible. Moreover, if all writes replicated copies of databases or remote networks and binding off, I want to write, has no effect on application availability. Of course, you can use the small local, while mandatory are written copies of the server type is optional. But mandatory and optional settings can be better served regular master-master configuration, which provides partial failure of the functionality of the deferred queue.http://www.dbametrix.com
Synchronous replication is most important sites of the network capacity, where the distances between geographical locations (involved in replication)
is not suitable too large. If possible, it is recommended that the application of a LAN to avoid unacceptable performance, and also to provide a reliable signal from the network, which is the physical proximity of the given machine replicates. WAN performance can also be used, provided that not more than a few hundred kilometers from each area (again, as a major disaster such as an earthquake, all pages cannot be removed). In all cases, the unreliability of transactions to implement a synchronous replication to replicate through the Internet, the Internet's voice signal. Private networks are highly recommended for the quality and reliability of the network behind the records. Abundant architectural analysis should be performed prior to the adoption and implementation of synchronous replication.http://www.dbametrix.net
This means that the application of the synchronous replication sites, which are located at a long distance is not easy. You can do a lot of things, such as bandwidth, logical corruption, some of the websites listed below, a long series of data errors and performance. These are common problems in the application. If you apply the same configuration is consisting of a network of private places where you can get the benefit of all, and solve simple problems.