IDoc (for intermediate document) is a standard data structure for electronic data interchange (EDI) between application programs written for the popular SAP business system or between an SAP application and an external program. IDocs serve as the vehicle for data transfer in SAP's Application Link Enabling (ALE) system. IDocs are used for asynchronous transactions: each IDoc generated exists as a self-contained text file that can then be transmitted to the requesting workstation without connecting to the central database. Another SAP mechanism, the Business Application Programming Interface (BAPI) is used for synchronous transactions.
A large enterprise's networked computing environment is likely to connect many geographically distributed computers to the main database. These computers are likely to use different hardware and/or operating system platforms. An IDoc encapsulates data so that it can be exchanged between different systems without conversion from one format to another.
IDoc types define different categories of data, such as purchase orders or invoices, which may then be broken down into more specific categories called message types. Greater specificity means that an IDoc type is capable of storing only the data required for a particular transaction, which increases efficiency and decreases resource demands.
An IDoc can be generated at any point in a transaction process. For example, during a shipping transaction process, an IDoc may be generated that includes the data fields required to print a shipping manifest. After a user performs an SAP transaction, one or more IDocs are generated in the sending database and passed to the ALE communication layer. The communication layer performs a Remote Function Call (RFC), using the port definition and RFC destination specified by the customer model. The IDoc is transmitted to the receiver, which may be an R/3, R/2, or some external system.