ALE has three prime entities, which participate in the message exchange process:
- SAP R/3 system
- ALE converter (inclusive of its sub-components)
- External non SAP R/3 system
The following diagram describes how these three work together in an ALE scenario.
Figure 2: ALE FUNCTIONALITY
Image Source:
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2.1 Concept of Logical Systems (LS):
Logical Systems represent R/3 or external systems in the SAP R/3 environment for the distribution of data. The existence of LS is mandatory for the corresponding R/3 client (which uses ALE or EDI). This LS acts as the "sender" for outbound messages and a "receiver" for inbound messages.
In addition to the base LS, another LS must be present within that R/3 system for each R/3 or external system used for ALE interfaces. In an inbound ALE interface, second LS represent the sender (another R/3 or external system) with respect to the base LS (receiver). In an outbound ALE interface, this second LS is the receiver on behalf of the R/3 or external system with respect to the base LS (sender).
2.2 Message Type:
Message types (required for sending the data across participating systems) relate to the structure of the data called an IDOC (Intermediate Document). Message types provide the format of the data, which can be exchanged between SAP and non-SAP systems. ALE supports over 200 message types in R/3.