The Telerik.Reporting.DatabaseSession assembly is intended for internal use only by the Telerik Reporting engine, when you are utilizing the Database Session State Provider. You are not supposed to add an explicit reference to it in your project, and it does not expose any publicly available functionality anyway. The correct method to configure the Database Session State Provider is described in the following help topic from the online documentation: Configuring the Database Session State Provider
. A more detailed explanation about the session state management system of Telerik Reporting can be found here: Session State Management
You are correct that the Database Session State Provider uses Telerik OpenAccess internally, however installing OpenAccess is not strictly required, since the Telerik.Reporting.DatabaseSession assembly contains a stripped-down version of the OpenAccess database engine embedded directly into it, and the references to the OpenAccess assemblies are resolved dynamically at runtime. This also explains why you receive compile-time errors when you add a reference to Telerik.Reporting.DatabaseSession in your project and you do not have OpenAccess installed.
the Telerik team