Replication Server maintains replicated data in multiple databases while ensuring the integrity and consistency of the data. It provides clients using databases in the replication system with local data access, thereby reducing load on the network and centralized computer systems.
The Replication Command Language (RCL) enables you to customize replication functions and to monitor and maintain the replication system. For example, you can request subsets of data for replication at the table, data row, or column level. This feature further reduces overhead by allowing you to replicate only the data that is needed at the replicate site.
Replication Server supports heterogeneous data servers. You can build a replication system from existing databases and applications without having to convert them. As your enterprise grows and changes, you can add data servers to your replication system to meet your needs.
Replication Server uses a basic publish-and-subscribe model for replicating data across networks. Users “publish” data that is available in a primary database, and other users “subscribe” to the data for delivery in a replicate database. Users can replicate both changes to the data (update/insert/delete operations) and stored procedures using this method.
Instructions to publish and subscribe to data are given at Replication Servers that control, or have a connection to, each database. The user creates a replication definition at a primary Replication Server, which controls the primary database containing the data to be published. The replication definition specifies information such as which columns are to be replicated, or in the case of a database replication definition, of the database objects to be replicated. The user creates a subscription at a replicate Replication Server, which controls the replicate database that will receive the information.
Replication Servers communicate with each other via user-defined routes. Most commonly, a primary Replication Server sends data to a replicate Replication Server through one or more routes set up to transmit data from the primary database to the replicate database. Users may also transmit stored procedures from the replicate to the primary to request updates of the primary data; in this case, data flows through one or more routes from the replicate Replication Server to the primary Replication Server.
Connections and routes define the structure of the replication system. They allow Replication Servers to send messages to each other and to send commands to databases. A connection transfers messages from a Replication Server to a database. A route transfers requests from a source Replication Server to a destination Replication Server.
