The following modification scenarios are possible:

1. You are using the standard IDoc but want to process the IDoc in accordance with your own requirements.
2. You are using the standard IDoc but want to modify standard IDoc processing, i.e. error handling is to be modified or the contents of the IDoc are to be interpreted in accordance with the individual requirements of the customer.
3. You are using a modified IDoc with your own segments and want to process the data from these segments in a certain way.
4. You are using a modified IDoc with your own segments and want to define the procedure for processing the IDoc yourself.
5. You are using your own IDoc with a new message type and have to define the procedure for processing the IDoc yourself.

The master function module filters the useful data for each IDoc and calls the actual processing function module in the application in a loop. A customer exit is implemented both immediately before and after this function module is called. You can use the exit after the call to update a user-defined error status or to change the set error status. You can use the exit before the call to carry out user-defined updates, for example, or to evaluate your own segments that you added to the IDoc definition. You can define your own IDoc segments in the IDoc maintenance transaction (/nWE30). Refer to the appropriate ALE group documentation.

The source code of the master function modules contain the names of the customer exits.

Make sure that no commit work is issued when generating your own function module or when using the customer exits as the function module branches back to the ALE service layer, after processing has been completed; application errors that have occurred are updated, the IDoc status is set and even rollbacks, should these be necessary, are performed here. After a commit work, it would no longer be possible to perform a rollback in the event of an error. This would result, in certain cases, in partially-posted IDocs and thus inconsistent error processing.

It should be noted that additional I/Os which take place in the customer exits can have a negative affect on performance.

If you create your own master function modules, the SAP system offers a series of general-purpose function modules for the various tasks to be performed. Refer also to the above master function modules with regard to this.

You can define your own IDoc (intermediate document type) in the same way as you maintain your own segments. This IDoc must be assigned to a new message type. You must maintain the partner profile for the new message type. The input tables must continue to be maintained in the transaction /uSALE. The standard task TS 0000 8049 can be used for error processing.

The following modifications can be made in the individual modification scenarios:

1. You can implement your own processing function module for processing the IDoc. This module can be copied from the standard function module of the respective message type and adapted accordingly.
2. You can activate the customer exits in the standard function module. You must activate and implement the customer exit for a user-defined error status if you wish to modify error handling. The customer exit for user-defined updates must be activated and implemented if IDoc processing is to be modified.
3. You can define your own IDoc segments in the standard IDoc and use the customer exit for user-defined updates to process data from your own segments.
4. You can define your own IDoc segments in the standard IDoc and implement your own processing function module as in scenario 1.
5. You can define your own IDoc segments and implement your own processing function module. The standard auxiliary function modules can be used when generating the function module.