Scope of the Upgrade Procedure
Before you start the upgrade, review the information about upgrading Extract and Replicat.
Even though you may only be upgrading the source or target, rather than both, all processes are involved in the upgrade. All processes must be stopped in the correct order for the upgrade, regardless of which component you upgrade, and the trails must be processed until empty.
Oracle recommends that you begin your upgrade with the target rather than the source to avoid the necessity of adjusting the trail file format.