What is Replication?

Replication is the process of maintaining copies of data in multiple databases. The purpose of replication is to make data highly available to applications with minimal performance impact.

In addition to providing recovery from failures, replication schemes can also distribute application workloads across multiple databases for maximum performance and facilitate online upgrades and maintenance.

Replication is the process of copying data from a master database to a subscriber database. Replication is controlled by replication agents for each database. The replication agent on the master database reads the records from the transaction log for the master database. It forwards changes to replicated elements to the replication agent on the subscriber database. The replication agent on the subscriber database then applies the updates to its database. If the subscriber replication agent is not running when the updates are forwarded by the master, the master retains the updates in its transaction log until they can be applied at the subscriber database.

An entity that is replicated with all of its contents between databases is called a replication element. TimesTen Classic supports databases, cache groups, tables and sequences as replication elements. TimesTen Classic also supports replicating XLA bookmarks.

The active standby pair configuration provides the highest availability. In an active standby pair replication scheme, the data is copied from the active database to the standby database before potentially being copied to read-only subscribers.

• An active standby pair is the only supported replication scheme for databases with cache groups.

• Certain DDL statements in an active standby pair are replicated against the other nodes in the replication scheme. See Making DDL Changes in an Active Standby Pair.