I Doc means Intermediate Document this is the terminology we
use in configuring in ALE (Application  Link Enabling). 

This ALE we use to transfer the Data from one Client to
another Client.

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Murali

IDOC INTERFACE:Standard SAP format for electronic data 
interchange between systems (Intermediate Document).

Different message types (for example, delivery 
confirmations or purchase orders) normally represent the 
different specific formats, known as IDoc types. Multiple 
message types with related content can be assigned to one 
IDoc type

Example:

The IDoc type ORDERS01 transfers the logical message types 
ORDERS (purchase order) and ORDRSP (order confirmation).

Among other areas, IDocs are used in both Electronic Data 
Interchange (EDI) and for data distribution in a system 
group (ALE).

A definition of formats (IDoc types) and methods (port 
definitions) for electronic data exchange between SAP 
systems and partner systems.

Partner systems can be any of the following:
A ERP System
An EDI subsystem 
Another R/3 system 
Another R/2 system 
Third-party software 
IDOC ADAPTER: IDOC Adapter is used to connect SAP 
components (or third-party systems) to an Integration 
Server by using IDocs (Intermediate Documents).

IDOC TYPE: An SAP format for transferring the data for a 
business transaction.

An IDoc is a concrete message formatted in the IDoc type. 
An IDoc type can usually transfer more than one different 
type of message: These are the logical messages, which 
correspond to different business processes.

Example

The order number 4711 has been sent to a supplier as IDoc 
no. 0815. IDoc number 0815 is formatted in the IDoc type 
ORDERS 1, and has the status records "created" and "sent". 
The purchase order corresponds to the "logical" message 
ORDERS
IDOC XML: IDoc (Intermediate Document) represented in XML 
down to segment level.


Example: BAI2 file formats( also called text or flat file) 
used in lockbox processing