You must start replication when the source and target data is in a synchronized state, where the corresponding rows in the source and target tables contain identical data values. Unless you are starting with brand new source and target databases with no current user activity, you will need to activate change capture and apply processes to handle ongoing transactional changes while an initial load is being applied to the target. This process is known as initial synchronization, or also as instantiation. The initial load captures a point-in-time snapshot of the source data and applies it to the target, while Oracle GoldenGate maintains any changes that are made after that point.

See Instantiating Oracle GoldenGate with an Initial Load in Administering Oracle GoldenGate for instantiation options.