Irrespective of the direction (R/2 ® R/3 or R/3 ® R/2) of communication, the data exchange takes place as follows:

Whenever a relevant transaction is posted, the system concludes that data needs to be transmitted to the companion system.

The transmitting system determines the destination system by means of a communication number.

The communication document is created by the respective application and placed into a special queue in an interim file called a DOUT.

The communication document is usually transmitted to the receiving system by means of an asynchronous procedure.

A transmission program (commonly called the "driver") is activated, which then sets up the connection to the receiving program and transmits the communication document via the CPI-C.

The communication document is received in the receiving system and placed into an interim table. The necessary postings are then executed automatically.