At present, there are a large number of enterprise database migration requirements to the cloud some customer databases on the cloud directly use the cloud database (B) after cutover, and the database under the cloud (A) only does historical data backup and is no longer used in production. Based on risk considerations, some customers need to have a data consolidation period after the business is switched over and used by the cloud database, that is, the online database is synchronized to the on-premises database (A or C) in real time to avoid problems with the cloud business and quickly fall back to the offline database. As a cloud architect, which of the following methods can be taken to achieve the requirements of the latter customer? Multiple selection