Enhancement

        SAP is a ERP software in which all standard business applications are delivered, sometimes customer may need to alter existing functionality or add additional functionality to the existing applications based on customer business requirements.

Enhancements concept :

          The enhancement is a concept of adding your own functionality to SAP's standard business applications without having to modify the original applications. To modify the standard SAP behavior as per customer requirements, we can use enhancement framework.

Types of enhancements in SAP :

User Exits

        Initially SAP implemented enhancements in the form of User Exits and these are only available in SD module, user exits are implemented in the form of subroutines and hence are also called as FORM EXITS, User exits are empty subroutines that SAP developers have provided for you, you can add your own source code in the empty subroutines.

All user exits starts with the word USEREXIT.

Customer Exits

        These are one type of enhancements that are available in some specific programs, screens and menus within standard SAP Applications. These are Function Modules with a custom empty include program, you can add your own functionality in these include programs.

Customer Exits are available in all SAP modules, whereas user exits are only available in SD module.

All customer exits ( Function Modules) starts with CALL CUSTOMER word.

BADI (Business Add-in) 

          BADI (Business Add-In) is a new SAP Object Oriented enhancement technique which is used to add our own business functionality to the existing SAP standard

functionality. 

              In Case Of BADI , We Can Create Multiple Instance Of The Class. BADI follows Object Oriented approach to make them reusable.

              For example if we assign an enhancement to one custom project, then that enhancement cannot be assigned to any other custom projects. To overcome this drawback SAP has provided a new enhancement technique called BADI.  

SE18 is the T-code for BADI definition.

SE19 is the T-code for BADI implementation.

Comparision With the exits.

• The main advantage of using BADI's is ,we can create multiple implementations for a single BADI definition.
• Where as with the exits, we can create a single implementation.i.e a single project for a enhancement.
• We cannot create another project (implementation) for enhancement which is already used. That is why we go for BADI's.

Types of BADI

•  Single implementation BADI.
•  Multiple implementation BADI.
•  Filter BADI.
•  Custom BADI (Not used/Rarely used)

Single implementation BADI:- A BADI which has only one implementation (single class) is called single implementation BADI. IN BADI Definition Properties type , If WITH IN SAP checkbox is selected then this BADI is only used by sap.

For Performing Single Implementation, Multiple use checkbox Should be uncheck.

Multiple implementation BADI:- A BADI which has multiple implementations is called multiple implementation BADI. By default all the implementations will be executed.We cannot control the sequence of execution of multiple implementations.
For Performing Multiple Implementation, Multiple use checkbox Should be check in BADI Definition
Filter BADI : It is type of BADI which has a filter value so that only those implementations which satisfy the filter value are executed. The remaining implementations are not executed this type of BADI is called a filter BADI.
For Performing Filter BADI, filter dependent checkbox should be check in BADI Definitions then it is filter dependent BADI.We need to specify the filter type such as land1,bukrs,werks.for the filter BADI.