During the upgrade, you must drop the source schema, re-create it from the target schema, and then import the database dump file. Do not attempt to bypass this process by applying a change list, because the schemas must be exactly the same in both databases for the replication to work. To avoid making inadvertent changes, enable Production Mode on the source and target databases. Log in to the Hub Console, select the Databases tool, select the database, and enable Production Mode. In future, if you need to apply a change list to the target database, you can disable Production Mode and apply the change list.