User exits are enhancement techniques in SAP that allow developers to insert custom logic into standard SAP programs without modifying the original source code. These exits are predefined hooks provided by SAP, enabling customers to tailor SAP functionality according to their business needs. Unlike BADIs, which are object-oriented, user exits are function module-based and follow the procedural programming model.

What are User Exits?

User exits are predefined enhancement points in SAP where custom code can be added. These exits are typically located within function modules and are invoked during standard business processes. They are a part of SAP’s legacy enhancement framework, primarily found in older versions like R/3 and ECC.

User exits are mainly used to:

• Add additional checks or validations.
• Modify data before it is saved.
• Influence the flow of standard SAP processes.

Types of User Exits in SAP

There are different types of user exits, each serving specific purposes. The most common types of user exits include:

1. Function Module Exits

Function module exits are one of the most common types of user exits. These exits allow developers to call a function module that contains the customer’s custom logic during a specific point in the standard process.

• How it works: SAP provides a specific function module with an EXIT_ prefix (e.g., EXIT_SAPLV56K_002), and this function module is empty by default. Developers can insert custom code in these function modules.
• Example: In the delivery processing program (SAPLV56K), a function module exit like EXIT_SAPLV56K_002 might allow developers to add custom logic to the delivery process.

2. Menu Exits

Menu exits enable developers to add custom menu options to SAP standard applications. These additional options can be linked to custom functions or screens.

• How it works: SAP provides a menu entry point where a customer can insert custom options into the standard menu bar or application toolbar.
• Example: In the Sales Order transaction (VA01), a custom menu option for specific checks can be added using a menu exit.

3. Screen Exits

Screen exits allow developers to add custom fields or screens to standard SAP transactions. This is particularly useful when additional data needs to be captured during a business process.

• How it works: SAP provides a subscreen or an area on a screen where customers can add custom fields or subscreens.
• Example: In the sales order creation transaction (VA01), a custom screen exit might allow developers to add additional tabs for specific business information.

4. Field Exits

Field exits allow developers to add custom logic for specific fields in SAP screens. This can be used for field validation or dynamic changes to the field’s properties (e.g., enabling, disabling, or defaulting values).

• How it works: SAP allows you to attach custom logic to a field using a function module that triggers during field input or validation.
• Example: A field exit could be used to validate the input in a sales order field, such as customer credit limit or product availability.

User exits offer a flexible way to enhance SAP standard processes without modifying the core code.