E3 basically uses two technologies to access Oracle Databases, ADO (ActiveX Data Object) and OCI (Oracle Call Interface).

ADO is a technology used by E3Browser and E3Chart to retrieve data stored in a Database. ADO is also widely used in E3 scripts for all types of operations with a Database. It is a set of COM (Component Object Model) objects created to access DBMS information, by using OLE DB (Object Linking and Embedding). This technology is available when installing OLE DB Provider for Oracle (MSDAORA) and allows access to Oracle's native interface, OCI.

OCI is used by E3's Database Server to implement Database services used by Historic objects, Formulas, Alarms, and Storage. With OCI, users have direct access to Oracle functions, making this process as optimized as possible. It provides a default Database access library and data retrieval functions as a DLL or LIB, which can be linked to an application at run time.