BAPIs are integrated into the ALE communication model. ALE communication is asynchronous and message-based. ALE communication is the preferred way to integrate distributed SAP Systems, for example, for distributing master data.

Since Release 4.0 BAPIs are the standardized interfaces for ALE-supported communication. ALE services, such as asynchronous BAPI calls, distribution model, monitoring and error handling can be used for BAPIs. The IDoc types required for the ALE services can be generated from BAPIs.

When you use BAPIs for asynchronous messaging, the application in the sending system calls the generated ALE IDoc interface instead of the BAPI. The ALE IDoc interface performs the following tasks:

• Creates an IDoc from the BAPI data
• Sends the IDoc to the target system
• Receives the IDoc in the target system, creates the BAPI data from the IDoc and calls the BAPI

You can use Transaction BDBG to create the other objects required for the asynchronous communication (message type, IDoc type, inbound and outbound function module).

A BAPI should only be implemented as an asynchronous interface, if at least of the following conditions is satisfied:

• Database changes are consistent in all systems
  Data must be updated consistently on a remote system as well as on the local system.
• Looser coupling
  With a synchronous interface the coupling between the client and the server system is too narrow. If the connection is interrupted the client system would not be able to function properly.
• Performance
  The interface has a large volume of data or database operations to be carried on the server system will take a long time. In this situation a synchronous interface cannot be used because performance would be too low.

BAPI/ALE integration requires that: