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Difference between IDocs, ALE, RFC and EDI in a SAP ERP system

IDoc – Intermediate Document

IDocs is the standard exchange format used for importing/exporting data into/from SAP systems. Business data such as master data, invoices, delivery notes and the like may be exchanged with external systems via IDoc interfaces. These external systems may be within the own company or data may be exchanged with systems belonging to other companies.

An IDoc interface has a defined data structure and IDoc processing logic. The detailed structure of IDocs was discussed in a previous article.

The SAP term for data exchange with other in-house systems is ALE (Application Link Enabling). The term EAI (Enterprise Application Integration) is also commonly used in non-SAP environments. ALE communication may be synchronous or asynchronous.

Data exchange to other companies is referred to as EDI (Electronic Data Interchange). EDI communication is message-based and thus always asynchronous.

The figure below shows an example of a scenario with ALE and EDI.

Difference between ALE and EDI
Difference between ALE and EDI

Customers and suppliers are linked to the SAP system via EDI. In-house third-party software such as CRM (Customer Relationship Management), HR (Human Resources) and PDM (Product Data Management) will be linked via ALE.

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ALE – Application Link Enabling

Within the framework of ALE, business processes take place distributed on different in-house IT systems. The systems are physically separate, and communication takes place between different Logical Systems (LS).

A logical system comprises specific software such as CRM systems. In SAP, a logical system is assigned to a client and has an own system name. Logical systems may in SAP be defined using Transaction BD54, as shown in the figure below.

Logical systems in Transaction BD54
Logical systems in Transaction BD54

Specific clients are assigned to a logical system via Transaction SCC4.

A distribution model must be set up to define which IDocs to exchange using which logical system. A distribution model may be defined using Transaction BD64.

ALE is based on RFC (Remote Function Call) for communication.

RFC – Remote Function Call

RFC is a process used to call up a function (also referred to as function module in SAP) in a remote system. Business logics may thus be called up in a third-party system.

RFC is thus in the SAP environment synonymous with Remote Procedure Call (RPC), but it is also used as an umbrella term for SAP interfaces and protocols used for the implementation of function calls.

A DESTINATION parameter is given when calling up a remote function module in ABAP. The following is an example of a call-up of the STORE_NEW_CUSTOMER function in the CRM4711 system.

      customer = cust
      crm_customer_id = id
      customer_exists = 1

A customer object is passed to this method, to store in the CRM system. The CRM system customer ID number is returned to, for instance, store with the master debtor data in the SAP system.

SAP distinguishes between four different types of RFCs:

  • Synchronous (sRFC)
  • Asynchronous (aRFC)
  • Tranactional (tRFC)
  • Queued (qRFC)

EDI – Electronic Data Interchange

Data exchange with other companies is referred to as EDI (Electronic Data Interchange). Instead of the direct exchange of IDocs, data will first be converted to a uniform exchange format, the so-called EDI format. Well known EDI formats include, for instance, UN/EDIFACT, ANSI ASC X12, VDA etc. and the corresponding derivatives and sub-standards.

An EDI converter is used for conversion between IDocs and the EDI format.

SAP systems do not use logical systems for electronic data exchange, but they define partners. These partners may, for instance, be customers or suppliers. The settings for specific partners are also called partner agreements and configured in Transaction WE60.

Any questions about SAP and EDI?

Any questions about SAP ERP, SAP SD and the associated EDI processes? Please contact us or check out our chat – we look forward to assisting you!


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