Persistency constitutes an important issue in software development and is of particular importance within object oriented design. However it seems that identification of persistent objects and their later design have not been given enough attention. The paper investigates one of UML-based software development process from the perspective of modeling persistency. Drawbacks of currently used typical approaches to modeling persistent data are identified and compared with mature techniques for database modeling. An improvement of the development process by providing means for modeling of persistency at early stages and introduction of data modeling technique into UML-based development process is proposed. The proposal is supported by a definition of UML persistent data modeling profile based on the usage of database technology for implementation persistency. Integration of the improvement with existing solutions for realization of persistency is also discussed.