Although not heavily discussed in this book, one of the main features of GoldenGate is its support for heterogeneous databases. GoldenGate's decoupled architecture and its trail file universal data format enables heterogeneity. This is the main selling feature for Oracle because GoldenGate does not require additional gateways or any conversion software in order to extract and replicate data across environments.

The decoupled architecture allows a database-specific flavor of the same version of GoldenGate software to be installed on each source and target server, enabling trail files to be written to in a common file format. Such files are subsequently consumed by the target server's apply process.

This is illustrated in the following diagram:

GoldenGate's decoupled architecture for heterogeneous databases

Unfortunately, the decoupled nature of heterogeneous data replication provides some limited functionality—for example, DDL replication is not supported. Oracle GoldenGate...