Nowadays maintenance of database management systems (DBMSs) often requires offline operations for enhancement of functionality or security updates. This hampers the availability of the provided services and can cause undesirable implications. Therefore it is essential to minimize the downtime of DBMSs. We present the CoBRA DB (Component Based Runtime Adaptable DataBase) project that allows the adaptation and extension of a modular DBMS at runtime. In this paper we focus on the definition of an adaptation model describing the semantics of adaptation processes.