Recently I got a job as ABAP/4 programmer. I don't know about User exits. Can you please help tell me about User Exits and how can I learn User Exits fast!
User exits are hooks in standard SAP code, which allow you to add
functionality. The positioning of these exits has been defined by SAP, so
often you can't find one where you need it!
The implementation of user exits depends on the module. Some (and more, as you go to later releases) are implemented using CALL CUSTOMER-FUNCTION (see help documentation for this ABAP statement) - these are controlled from transactions CMOD and SMOD - have a look at the online documentation - transaction CMOD, menu Utilities --> Online Manual.
In older areas of SAP code, the exit might be coded using an empty form supplied by SAP. E.g. look at module SAPMV45A. This has many forms beginning USEREXIT_... You can insert your own code in this.
In other areas such as FI or LIS, there are configuration entries which allow calls to external ABAP code.
Up until 4.5, there are field-exits. These are triggered as the first action during a PAI event. They are linked to a field's domain, and can be made global for that domain, or screen specific.
Finally, you may need to make customer specific changes to SAP code. Note that if you choose to do this, SAP will not support the modified code.
This was first published in September 2001