Continuous access to an application and associated data is provided during a modification (for example, an upgrade) of the application. Shared tables are used to perform parallel changes in databases associated with an original database schema, a temporary database schema, and an upgraded database schema. Aliases are used to access shared tables from some database schemas. The use of shared tables obviates a separate merging of data written by different tools and/or systems during an upgrade of the application. Related methods, apparatuses, systems, techniques and articles are also described.