This paper describes a framework that supports the simultaneous evolution of objectoriented data models and relational schemas with respect to a tool- supported object-relational mapping. Thereby the proposed framework accounts for non-trivial data migration induced by type evolution from the outset. The support for data migration is offered on the level of transparent data access. The framework consists of the following integrated parts: an automatic model change detection mechanism, a generator for schema evolution code and a generator for data migration APIs. The framework has been concepted in the IMIS project. IMIS is an information system for environmental radioactivity measurements. Though the indicated domain especially demands a solution like the one discussed in the paper, the achievements are of general purpose for multi-tier system architectures with object-relational mapping.