Oracle replication has been around for quite some time and has become a mature, feature-rich environment to satisfy widely dispersed processing requirements. Replication was first introduced as a way to allow Oracle tables or subsets of tables to be available locally on widely separated database servers. This was accomplished via the use of snapshots (point-in-time copies) of required tables that were copied from a master server to one or more remote slave servers. The snapshot technique was particularly effective for relatively static tables that did not require frequent refresh operations to be kept in sync with the master tables. Read-only applications benefited from the use of snapshots since wide-area network transmission time was eliminated, significantly improving performance.
Snapshots are now more commonly known as materialized views, and while the creation of remote materialized views of master tables is still a common use of replication, the technology has matured significantly, supporting a much broader spectrum of database objects. I'll discuss the snapshot method and then explore more advanced techniques.
The article continues at