Transforming a database while allowing the data in the database to be available to database users during the transformation of the database. A method includes creating a new version of metadata for an old copy of database items. The method further includes creating a copy of data items to be transformed in the old copy of database items while applying a transformation to the data while migrating data from the old copy of database items to the new copy of database according to the new version of metadata. The method further includes while migrating data from the old copy of database items to the new copy of database items, servicing user queries made against the old copy of database items to allow the database to remain online while transforming data items in the database.