What is the use of change pointer concept in ale?

Question

what is the use of change pointer concept in ale?
Edited by: Alvaro Tejada Galindo on Feb 6, 2008 5:10 PM

Answer 1

ALE Architecture:
It consists of an Outbound process, an Inbound process, and an Exception – Handling process.
Outbound Process:
ALE Outbound Process in SAP sends data to one or more SAP Systems. It involves four steps.
1. Identify the need of IDoc: This step starts upon creating a application document, can relate to a change to a master data object.
2. Generate the Master IDoc: The document or master data to be sent is read from the database and formatted into an IDoc format. This IDoc is called as a Master IDoc.
3. Generate the Communication IDoc: The ALE Service layer generates a separate IDoc from the Master IDoc for each recipient who is interested in the data. Separate IDocs are generated because each recipient might demand a different version or a subset of the Master IDoc. These recipient-specific IDocs are called Communication IDocs and are stored in the database.
4. Deliver the Communication IDoc: The IDoc is delivered to the recipients using an asynchronous communication method. This allows the sending system to continue its processing without having to wait for the destination system to receiver or process the IDoc.
Inbound Process:
The inbound process receives an IDoc and creates a document in the system.
1. Store the IDoc in the database: The IDoc is received from the sending system and stored in the database. Then the IDoc goes through a basic integrity check and syntax check.
2. Invoke the Posting Module: The control information in the IDoc and configuration tables are read to determine the posting program. The IDoc is then transferred to its posting program.
3. Create the Document: The posting program reads the IDoc data and then creates a document in the system. The results are logged in the IDoc.
Over view of IDocs:
IDoc is a container that is used to exchange data between any two processes. The document represented in an IDoc is independent of the complex structure SAP uses to store application data. This type of flexibility enables SAP to rearrange its internal structure without affecting the existing interface.
IDoc interface represents an IDoc Type or IDoc data. IDoc Type represents IDoc’s definition and IDoc Data is an instance of the IDoc Type.
IDoc Types:
IDoc type structure can consist of several segments, and each segment can consist of several data fields. The IDoc structure defines the syntax of the data by specifying a list of permitted segments and arrangement of the segments. Segments define a set of fields and their format.
An IDoc is an instance of an IDoc Type and consists of three types of records.
i. One Control record: each IDoc has only one control record. The control record contains all the control information about an IDoc, including the IDoc number, the sender and recipient information, and information such as the message type it represents and IDoc type. The control record structure is same for all IDocs.
ii. One or Many Data records: An IDoc can have multiple data records, as defined by the IDoc structure. Segments translate into data records, which store application data, such as purchase order header information and purchase order detail lines.
iii. One or Many Status records: An IDoc can have multiple status records. Status record helps to determine whether an IDoc has any error.
Message in IDoc Type:
A Message represents a specific type of document transmitted between two partners.
Outbound Process in IDocs:
Outbound process used the following components to generate an IDoc. A customer model, and IDoc structure, selection programs, filter objects, conversion rules, a port definition, an RFC destination, a partner profile, service programs, and configuration tables.
The Customer Model:
A customer model is used to model a distribution scenario. In a customer model, you identify the systems involved in a distribution scenario and the message exchanged between the systems.
Message control:
Message control is a cross application technology used in pricing, account determination, material determination, and output determination. The output determination technique of Message control triggers the ALE for a business document. Message control separates the logic of generating IDocs from the application logic.
Change Pointers:
The change pointers technique is based on the change document technique, which tracks changes made to key documents in SAP, such as the material master, customer master and sales order.
Changes made to a document are recorded in the change document header table CDHDR, and additional change pointers are written in the BDCP table for the changes relevant to ALE.
IDoc Structure:
A message is defined for data that is exchanged between two systems. The message type is based on one or more IDoc structures.
Selection Program:
Is typically implemented as function modules, are designed to extract application data and create a master IDoc. A selection program exists for each message type. A selection program’s design depends on the triggering mechanism used in the process.
Filter Objects;
Filter Objects remove unwanted data for each recipient of the data basing on the recipients requirement.
Port Definition:
A port is used in an outbound process to define the medium in which documents are transferred to the destination system. ALE used a Transactional RFC port, which transfers data in memory buffers.
RFC Destination:
The RFC destination is a logical name used to define the characteristics of a communication link to a remote system on which a function needs to be executed.
Partner Profile:
A partner profile specifies the components used in an outbound process(logical name of the remote SAP system, IDoc Type, message type, TRFC port), an IDoc’s packet size, the mode in which the process sends an IDoc (batch versus immediate), and the person to be notified in case of error.
Service Programs and Configuration Tables:
The outbound process, being asynchronous, is essentially a sequence of several processes that work together. SAP provides service programs and configuration tables to link these programs and provide customizing options for an outbound process.
Creation of IDoc:
Basic Type:
Basic IDoc type defines the structure and format of the business document that is to be exchanged between two systems.
Segments:
Segments form the basic building blocks of an IDoc type and are used to store the actual datta. A segment type is the name of a segment and is independent of the SAP elease. A segment definition is the release-specific name of a segment.
Steps in creating Segments:
T.Code WE31
Enter the name for your segment type and click on the create icon.
Type the Short text.
Enter the variable names and data elements.
Save and Go back.
Go to Edit -> Set Release.
Repeat the steps to create more segments.
IDOC TYPE:
Business data is exchanged with an external system using the IDoc Interface.
IDoc types (Special Structures) An IDoc type is defined through its permitted segments. Segments can be dependent on each other (parent and child segments). The IDoc interface can check for each IDoc whether thhe segments contained are compatible with thhe definitiion of its type. This systax check is activated or deactivated in the Partner Profiles.
Steps in creating IDoc Type:
T.Code WE30 to create IDoc Type.
Enter the Object Name, Select Basic Type and click Create Icon
Select the create new option and enter a description for your basic IDOC type and press enter
Select the IDoc name and click Create icon
The system prompts us to enter a segment type and its attributes
Choose the appropriate values and press enter
The system transfers the name of the segment type to the IDoc editor.
Follow these steps to add more number of segments to Parent or as Parent-child relation.
Save it and go back.
Go to Edit -> Set Release.
Message Type:
Steps in Creating Message Type:
T.Code WE81.
change the details from Display mode to Change mode
After selection, the system will give this message "The table is cross client (See help for further info)". Press enter.
Click New Entries to create new Message Type.
Fill details
Save it and go back.
Assign Message Type to IDoc Type:
T.Code WE82
Change the details from Display mode to change mode.
After selection, the system will give this message "The table is cross client (See help for further info)". Press enter.
Click New Entries to create new Message Type.
Fill details
Save it and go back.
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Edited by: Alvaro Tejada Galindo on Feb 6, 2008 5:10 PM