SAP SD User Exits

Ways to find Enhancements/User exits

In SMOD find options of screen, menu, function exits.
Go to SE81 and select the relevant module find the enhancement.
Go to the program or transaction and search for “CALL CUSTOMER-FUCTION” or “EXIT__nnn”
For screen exits go to screen in SE51/SE80 search for- “CALL CUSTOMER-SUBSCREEN..”

User Exits & Customer Exits :

User Exits: These are subroutines used in the SAP namespace 'hard-coded' at various points within SAP Repository objects.

Customer Exits :

1. Menu Exits: Menu exits add items to the pull down menus in standard SAP applications. You can use these menu items to call up your own screens or to trigger entire add-on applications. These special entries have function codes that begin with "+" (a plus sign).

2. Screen Exits: Screen exits add fields to screens in R/3 applications. SAP creates screen exits by placing special sub screen areas on a standard R/3 screen and calling a customer sub screen from the standard screen’s flow logic. It is called by call customer- sub screen

3.Function Module Exits :Function module exits add functions to R/3 applications. Function module exits play a role in both menu and screen exits. When you add a new menu item to a standard pulldown menu, you use a function module exit to define the actions that should take place once your menu is activated. Function module exits also control the data flow between standard programs and screen exit fields.
It is called by Call Customer- function