Nowadays, implementing the Business-Data layers interaction is assisted by industry tools that provide abstraction on top of concrete database systems, but still requires writing a large amount of annoying bug-infected code. Full automation of the Business-Data layers interaction will provide a great improvement in complex systems development. We claim that automatic integration of the Business-Data layers requires careful analysis of navigational structures that involve persistency concerns in the Business layer. Therefore, our approach consists of a set of independent Data Access Patterns, each applying to a specific navigational structure. Moreover, the patterns are Business layer transparent, i.e., the Data layer interaction leaves the Business layer intact. In this paper we introduce two Data Access Patterns termed Persistent-to- Persistent patterns that handle navigational structures between classes that are both marked as persistent. The patterns are notable for their handling of Persistent-to-Persistent interaction, where all data is persistently stored. All patterns are based on a core Proxy Data-Mapper pattern, that is shortly described.