CDC: a publish/subscribe principle

The CDC architecture is based on the publisher/subscriber model.

The publisher captures the change data and makes it available to the subscribers. The subscribers utilize the change data obtained from the publisher.

The main tasks performed by the publisher are:

• identifying the source tables from which the change data needs to be captured.

• capturing the change data and storing it in specially created change tables.

• allowing subscribers controlled access to the change data.

In Trigger mode, or the AS/400 Redo/Archive log mode (journal), the subscriber is a table that only lists the applications that have access rights to the change tables. In the Oracle Redo/Archive log mode, the subscriber is a user of the database. The subscriber may not be interested in all the data that is published by the publisher.