Systems and methods include execution of a first application associated with a first access schema and a first data model in a data schema of a database system. While the first application is receiving incoming user requests, the first data model in the data schema is extended based on a second data model of a second application, a second access schema of the second application is prepared in the database system, data of the first data model in the data schema is migrated to the second data model, data of the first data model in the data schema is replicated to the second data model while the first application is receiving incoming user requests, the second application is executed, the incoming user requests are re-directed to be received by the executing second application, and the replication of data of the first data model in the data schema to the second data model is stopped. While the second application is receiving incoming user requests, data of the second data model in the data schema is replicated to the first data model.