Replication Using a Hub

When replicating using a hub configuration, the Oracle GoldenGate instance runs on an individual Server, Instance (like a compute instance), or Host and connects remotely to the database. This case is used mostly when you want to limit the overhead of Oracle GoldenGate on the source or target databases, or the database environment does not allow the software to be installed locally on the database server.

Most remote Extracts, except for SQL Server, can tolerate up to 80ms round trip ping time between the source database and the server where the Extract process is running. This provides a lot of flexibility in deciding where the server running the Extract process can be physically located. This feature enables capturing remotely in mutiple scenarios, especially for cloud databases. For example, it allows capturing remotely where the Extract process is running on a compute node in the same region, or in an on-premises data center, or in another region or cloud provider providing the network ingress and the egress is configured to allow for the client connection.

For best performance, Oracle recommends running the Extract process as close to the source database as possible.

Remote Replicats are highly dependent on low network latency because each network operation requires an acknowledgement before the next can be issued. Oracle recommends that the round-trip ping time between the server running the Replicat process and the target database be as low as possible, and typically any values higher than 4 ms will increase the Replicat lag.

In hub models, both the Extract and the Replicat for the same replication stream are deployed on the same server, so, there is no need for a Distribution Path. The Extract writes to a local trail file, and the Replicat reads from that same trail file. However, in some topologies, a hub might be deployed close to the source database, with an additional hub located near the target database. In these cases, changes are routed through the Distribution Path from the source hub to the target hub.

In the following diagram of a hub deployment, the Extract and Replicat processes operate from the same Oracle GoldenGate server and connect remotely to the source database.

This configuration can have multiple Oracle GoldenGate installations with multiple deployments managing a fleet of replication streams with similar or different topologies and use cases.