What is ALE
ALE stands for Application Link Enabling and is a remote connection technology .its allowing the decentralization of business processes by connecting decentralized systems together.Using ALE, it is easy to synchronize several SAP systems so that they contain the same data objects at any time. These objects may be master data (customers, vendors, Pricing, Condition GL accounts, cost centers,) or transaction data (FI documents, purchase orders,sales order). To enable the synchronization, ALE supports not only mass transfer of data between systems but also selective data transfers of objects changed since the last transfer.
How does ALE work?
High level Overview, the process is straight and simple: basically sender system selects the data that needs to be distributed, packs it in a standard format and sends it to one or several receiving systems. When a receiving system gets the data, it unpacks the standard format and records the data. There are several international standard procedure already available
In fact, There are 3 layers are involved in this process:
- An application layer which selects and records data in R/3.
- A distribution layer which filters and converts data.
- A communication layer which ensures the actual communication of records generated in a standard format.
The senders system system and receivers system are determined thanks to a so-called distribution model which defines the transfer rules (who sends what to who?). The definition of the distribution model must be known by all systems involved (either as sender or receiver) and must consequently exist on all those systems.
The Intermediate Document (IDoc)
Idoc is a intermediate document .Basically it is a structure Data container .The data transferred using ALE/EDI must have a SAP standard format to be understood from all partners in the communication. This format is the Intermediate Document (IDoc) which represents an intermediary structure between raw SAP data and EDI formats. This structure is not constant, it depends on the data to be transferred and SAP provides the structures for most SAP standard objects such as customers master data, sales orders, ...
An IDoc with a specific structure is said to have a specific type. The IDoc type is nothing more than a version of a specific IDoc structure designed to contain data for a specific object type. For example, the IDoc type DEBMAS05 is the fifth version of a structure that represents a customer master data. The management of versions for IDocs structures is necessary because the objects evolve with time and tend to become more and more complex with new data fields or tables being added regularly.
The conversion of raw data forth (for the sender system) and back (for the receiver system) to the IDoc format is also ensured by SAP standard function modules as long as you transfer standard objects. For non standard objects (enhancements), you must define your own IDoc structure and write your own conversion function modules.
RFC connections
The data communication between the SAP servers may be done by several ways. The 2 most simple ways are the transactional RFC and the file server or AL11. The RFC connection is used to make a direct connection between servers while the file interface speaks for itself, it uses a file containing the IDocs from the sender system as input in the receiver(s) system(s).
The selection of a communication method is made though the ports configuration as we will see in the next section. For the purpose of this article, we are going to choose the most efficient method: the transactional RFC method. To set it up, we first need to define the RFC destinations of the partner systems.
An RFC destination may be seen as a set of settings necessary to connect to a system using the RFC protocol. These settings include the address and type of the partner system along with connection information such as the user ID and password to use.
The RFC destinations of all partners systems must be defined on all systems to include in the distribution model. The transaction to use for this purpose is SM59
Definition of the communication ports
The communication ports determine the type of data communication that must occur between systems. When the communication is to use the RFC protocol, transactional RFC ports must be created specifying the RFC destinations of the partner systems. Use transaction WE21 for this purpose.
