An initial load synchronizes the source and target databases, which is an important first step in data replication. Commonly known as instantiation, it extracts an entire copy of the source dataset, transforms it if necessary, and applies it to the target tables. Data replication can then continue from this point.

One of GoldenGate's many features is change synchronization that keeps track of ongoing transactional changes while the initial load is being applied. This feature is used extensively as part of the supported zero downtime migration functionality, and when configured, the change data capture and delivery concurrent process tracks the incremental changes, which are then reconciled with the results of the initial load.

So why is instantiation so important? To answer this question, consider an UPDATE statement. By its nature, the row to be updated must exist on the target table; otherwise, the transaction will fail. This is also true for DELETE operations...