Object-oriented (OO) databases have happened important for both research and development area in the past decade. On the other hand, databases of this type have been found too expansive and not too functional in a planty of practical tasks. New architectures appeared: object-relational data managers, relational wrapper libraries, and OO databases. The attractiveness of these solutions is that enable OO applications to be written against today's enterprise data both file- and relation-oriented. Moreover, they make OO design methodologies available for implementing business objects. Our solution of persistence of C++object includes possibilities: to handle persistent objects via C++ prgrams, to conceive rows of relations as C++ objects, to use high-level query facilities in C++ programs, and to use many of database-oriented features on the level of C++ programming. The article is focused on some implementation techniques used in the GEN.LIB - a library managing a persistence through relations stored in a commercial RDBMS. The results are a part of the COPERNICUS project ADOORE.