General Communication Process - SAP WM

Link from Storage Location to R/3 Warehouse Number
In the R/2 System, the RM storage location is linked to the R/3 warehouse number via an assignment table, similar to the procedure for integrated processing . Warehouserelevant transactions that are posted in an R/2 storage location initiate a communication process between the two systems.

Link from Storage Location to R/3 Warehouse Number

Linking Two or More Plants to the Same Warehouse Number
As illustrated below, it is also possible to link two or more plants with their corresponding storage locations to the same warehouse number in the R/3 Warehouse Management component.

Linking Two or More Plants to the Same Warehouse Number

Master Data
In the R/3 Warehouse Management (WM) component, the master data is distributed between the two systems involved as follows:

Master Data in R/2
In the R/2 System, the material master contains all the data that is required for Inventory Management (RM) and the other integrated applications. The RM stock figures are maintained in R/2 only. The material master in R/2 does not contain any WM data for the storage location managed in the R/3 System.

Master Data in R/3

  • Warehouse master and quants
    The individual storage bins and the material stock (quants) are managed in the R/3 System. You can display the bin stock figures in this system as well.
  • Material master
    In R/3 you also maintain a material master record for each material managed in your warehouse. The material master data is required for transactions in Warehouse Management. For example, the system displays the material short text from the material master record when a transfer order is being processed.

The R/3 material master only contains data that is required for Warehouse Management. Data in the R/2 material master that is relevant for Warehouse Management (for example, the material short text, the stockkeeping unit) is transferred to the R/3 material master and may be maintained in R/3. Warehouse data that exists in R/3 only (for example, storage unit loading instructions) is maintained in R/3. In this way, you can be sure that data common to both systems does not differ in any way.

Goods Movement Data
Warehouse-relevant documents are posted in both systems:

  • Documents from the integrated applications, such as RM documents, deliveries, production orders, and so on, are posted in the R/2 System.
  • Only documents relating to Warehouse Management are posted in R/3, for example, transfer requirements, transfer orders and posting change notices. Usually, transfer requirements and posting changes are created automatically as a result of an R/2 posting.

Inventory Data
As in the integrated application, inventory is executed in the R/3 WM component based on the storage bins. Inventory differences found during an inventory procedure are transferred to the Inventory Management component.

When Does Communication Take Place?
If data is changed in one system (R/2 or R/3), or if documents that affect the other system are posted, the relevant data is transferred to the companion system. The direction of the communication (R/2 _ R/3 or R/3 _ R/2) varies, depending on the transaction. The direction is determined by the system that initiates the process. Communication between the two systems takes place with the following transactions :

When Does Communication Take Place?

Material Master Changes
Material master maintenance (creating new material master records or changing existing material master records) is always initiated in the R/2 System. Afterwards, the material master data is transferred to R/3.

Goods Transfers
Goods transfers such as material deliveries or material issues must be processed both in Inventory Management as well as in Warehouse Management. As a rule, the RM document is first posted in R/2. Afterwards, the transfer order is created in R/3. This process can also, however, be initiated by the R/3 System since it is possible with goods receipts and goods issues to create the transfer order first in R/3. The transfer data is transferred to R/3 and the RM document posted automatically.

Processing Deliveries
The deliveries are created in the R/2 Sales and Distribution (RV) component. As soon as the delivery data has been transferred to the R/3 system, the transfer orders for picking are created. After the transfer orders have been executed, the picked quantities are confirmed in the R/2 System so that the goods issue posting in R/2 is possible. This is a bi-directional process (R/2 → R/3 → R/2).

Difference Posting
If you enter differences in the R/3 System during the confirmation of a goods transfer, these are transmitted to the R/2 System.

What Data is Transmitted?
The entire document is not transmitted, only the data that is relevant for the companion system. A data extract is automatically created from the respective document (for example, the GR document). This extract is then transmitted to the companion system in the form of a communication document. Tables control which data is to be included in a communication document.

Communication Process R/2 -> R/3
The general communication process R/2 → R/3 is illustrated below.

Communication Process R/2 -> R/3

Storage Location Linked to Warehouse Number ?
If a posting in R/2 is relevant for the warehouse (for example, goods receipt), the system checks whether the storage location is linked to an R/2 warehouse number.
Creating a Communication Document in R/2
If there is a link to an R/2 warehouse number, the system creates a communication document in R/3 format. This document contains all the information relevant for Warehouse Management.
Downloading the Communication Document to R/3
The communication document is transmitted to the R/3 System and received there by a receiving program. Based on this communication document, the system executes the necessary postings (for example, transfer requirement, quant to interim storage area, material master change) in the WM component.

Communication Process R/3 -> R/2
The general communication process for R/3 → R/2 is illustrated below.

Communication Process R/3 -> R/2

If you post a goods movement in Warehouse Management (R/3) first, and then in Inventory Management (R/2), the communication process is as follows:

Creating a Communication Document in R/3
If you execute a posting in Warehouse Management that is relevant for inventory (for example, transfer order for stock placement), a communication document is set up in the R/3 System.
Uploading the Communication Document to R/2
Depending on your system configuration and host availability, the communication document is uploaded immediately, or at a later time, to the R/2 System and received there by a receiving program that executes the necessary postings in R/2.

Technical Communication Process
Irrespective of the direction (R/2 → R/3 or R/3 → R/2) of communication, the data exchange takes place as follows:

Technical Communication Process

Checking the Link
Whenever a relevant transaction is posted, the system concludes that data needs to be transmitted to the companion system.
Determining the Receiver
The transmitting system determines the destination system by means of a communication number.
Creating the Communication Document
The communication document is created by the respective application and placed into a special queue in an interim file called a DOUT.
Transmitting the Communication Document
The communication document is usually transmitted to the receiving system by means of an asynchronous procedure. A transmission program (commonly called the "driver") is activated, which then sets up the connection to the receiving program and transmits the communication document via the CPI-C.

Receiving the Communication Document
The communication document is received in the receiving system and placed into an interim table. The necessary postings are then executed automatically.

Terms that Apply to the Communication Process
The following terms are used frequently in connection with the R/3 Warehouse Management (WM) component.

Communication Document
The communication document forms the central element of the communication process. If data needs to be transferred between the two systems, a communication document is always created for the transmission process.

A communication document is a data chain that is transmitted for a transaction. It consists of communication records that all have the same record number. The first and the last record of a communication document are marked as such. In this way, the communication document forms a closed, logical unit.

Communication Record
A communication record is a data extract in R/3 format that consists of the individual data to be transmitted.

Record Type
Because different data has to be transmitted, depending on the transaction involved and the direction of the communication process, communication records are assigned to a record type.

Record Identification
A communication record is identified by its record type and its record number. Communication records with the same record number, irrespective of their record type, together form a communication document.

Data Structure
The structure of a communication document is stored in the Data Dictionary of both systems in R/3 format and depends on the record type. A separate table is defined for each record type. This table stores the corresponding communication records.

R/3 Format
Irrespective of the communication direction, the communication records are always transmitted in R/3 format. The record structure is identical in the R/2 and R/3 Data Dictionary. The decoding of the data always takes place in the R/2 System.

In this way, the companion system is always responsible for the data conversion. For this reason, it is unimportant to WM which system functions as the companion system (R/2 host, non-SAP host).

Record Types
The table below displays an overview of the record types, the tables in which the individual communication records are stored, and the usage of the individual communication records.

Overview of Record Types

Overview of Record Types

Status of Communication Records
When a communication document is created, the communication records are given a record status for the technical transmission process. On the basis of this status, the system can determine the position of each communication record within the communication document. The possible record statuses are listed in the table below:

Status of Communication Records

Status of Communication Records

Communication Number
If the system discovers during a transaction that a communication document is to be created, it first determines the receiver on the basis of a communication number. A communication number is the technical definition of the receiver (destination system, application, client, receiving program, and so on). The key for the queue file "DOUT" is determined by means of the communication number.

Queue ("DOUT")
The queue is in an interim file (called DOUT) in the transmitting system. The communication records to be transmitted are stored here before the transmission takes place. The communication documents can be sent from the DOUT file to the companion system either automatically or manually.

Transmission Program
There is a program (the so-called "driver") that is responsible for the transmission of communication documents to the partner system. If transmission takes place, the program performs the following tasks:

  • It sets up the connection to the receiving program in the destination system.
  • It transmits the communication documents from the DOUT file to the destination system via CPI-C. To activate the driver program, there are various possibilities, depending upon the system (R/2 or R/3).

The driver can be started

  • manually
  • automatically
  • as a batch process

Receiving Program
In the receiving system, the communication document is received by a receiving program. The receiving program performs the following functions:

  1. It writes the individual communication records in the table that was defined for the corresponding record type (see Mail Control in the R/3 System.)
  2. A status record (LDK00) is created for each communication record that serves to monitor the communication process.
  3. It checks the data contents of the communication records.
  4. It initiates the postings in the receiving system.

Receiving Tables
The communication records that are transmitted in a communication document are placed into interim storage in the receiving system (R/3) in the table defined for the respective record type As soon as the postings required for a communication record have been carried out, the system marks the communication document accordingly.

Status Table LDK00
In order to monitor the communication process, a status record is entered for each communication record in table LDK00 of the receiving system when the communication document is received. If the receiving system could not process the communication record, this fact is noted accordingly in the status record.

Communication Technique
Communication between the R/2 and R/3 systems always takes place based on asynchronous CPI-C. By asynchronous, we mean that communication documents are not sent directly or immediately from one system to another. Instead, they are assigned to a queue and the system attempts to send them as soon as the receiving system becomes available. CPI-C is an independent Price List component belonging to the SAP basic system and is described in detail in the BC SAP-Communication: Programming Guide.

Error Prevention Mechanisms
Error prevention mechanisms are built into the system for the transmitting of communication documents. These mechanisms make sure that:

  • A communication document is transmitted only once.
  • Incorrect communication documents do not interrupt the connection.
  • Communication documents that invoke a logical error are marked as incorrect and stored in an interim table.
  • In this way, errors can be analyzed at a later point and error recovery is possible.

Once-Off Data Transfer
Since communication records are placed into interim storage in the receiving system, the system can check upon receipt of a record whether this record has already been transmitted. If the record was already transmitted and processed once before, the system does not execute any further postings. If the record was transmitted once before, but not processed further, the system marks the record accordingly.

Error Recovery
If a logical error occurs during the processing task, the system marks the communication document as incorrect in an interim table. In addition, a Mail message pointing out the error is sent to the R/3 or R/2 System user(s) responsible (depending upon the direction of the communication).

The person responsible analyzes the communication document on the basis of the Mail information. As soon as the error has been recovered, the user starts the receiving program again using a transaction in order to repost the communication document.


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