The ADC can be used for integrating a DP4 application into a communications service to a remote computer. This may be a remote mainframe providing transaction services or perhaps a card validation service. Using this method, you create tables on the database that represent the communications service. Application accesses to these tables do not store data in the tables, but instead your own ADC processing invokes the communications services. This approach enables you to model the communications system as a set of tables, allowing the application programmer to remain largely unaware of the technicalities of the communications service. It also allows application development to continue without a communications link by using the tables directly to simulate dialog.
For example, you could create two tables called SEND_TX_REQ and TX_RESP which represent the actions of sending a transaction request and reading the response. They contain fields that you wish to send and receive from the communications service. Application programmers would write records into SEND_TX_REQ and read records from TX_RESP to invoke communications. Your ADC code would intercept accesses to these two tables, turning writes on SEND_TX_REQ into message transmits and reads on TX_RESP into a wait for response.