DP4 provides four tools for handling connections:
The OSDI is a tool to help you integrate devices such as scanners and journal printers into your database system
The Auxiliary Database Controller pack is is a tool to let you add extra features to the database manager. For example, you can add code to re-direct updates to a non-DP4 database or file system
Various ADC components are available which allow you to access non-DP4 database systems such as Oracle and Microsoft Access as though they were DP4 databases.
Message Manager is a tool to format data for sending to and receiving from a host system. For example, your application may read customer information from a host computer
All of these tools help you to make full use of the resources on your system by adding extra layers of functionality to your application. You can use these tools to integrate code that is developed and tested independently from your application programs. This method helps you develop your application in three ways:
When you develop your application program, you need not have any specialised knowledge of the OSDI pack or auxiliary database manager
Your application database and programs remain operating system and device independent
Your device driver, database system and message manager code can be tested separately from the application