Enhancement concept in SAP

SAP Provides five types of enhancement techniques. These are the ways to deviate/enhance from the SAP provided code/logic.


User Exits: The first type of modification/enhancement technique introduced by SAP. This is predominantly available in SD module and very rare in other modules. This is in fact a modification to SAP code, hence needs "Access Key".Through user exits changes can be done only to code (thus business logic), not to screens or menus. SAP provides empty FORM - ENDFORM routines, in which programmer can write his code. You can search for a user exit in a program using the key word "USEREXIT"

Customer Exits: This was the next type of technique provided by SAP after user exit. This is available generally in all modules. Unlike User Exits, this is not a modification, hence you do not require an access key to implement it. In addition to code changes, you have option to enhance screens and menus as well. SAP provides Z includes which get called by standard code. Programmers write the code in this Z include. You can search for a customer exit using the key word "CALL CUSTOMER"

BADI (SE18) 
BADI is a relatively new enhancement concept based on OOPs. BADI’s are predefined with an adapter class. Developer’s will create an instance of the adopter class of the BADI.
BADI will have a standard interface which describes the methods and parameters. A custom class needs to be created which will implement this interface.

Finding a BADI
a. In Status -> Program search for CL_EXITHANDLER
b. SPRO -> Business Add in

Multiple implementations possible? (SE19)
a.      You can make create implementations based on filter values. For Example, each country you can create different implementations. The filter value should be linked to a data element which should be linked to a domain. The domain should have fixed values.
b.      While defining if you select checkbox ‘Reusable’, then multiple implementations can be created and multiple implementations can be active and called. Else multiple implementations can be created but only one will be active anytime.

Enhancement Spots:Explicit and Implicit enhancement points
Implicit are available for all SAP programs at specified generic places. For example, After/Before all standard selection screen declaration, after all subroutines implementation, end of reports, beginning of FORMs, end of FORMs etc.
An enhancement spot can be two types. 1. Code 2. BADI
Explicit are SAP provided hooks/places where custom logic can be written.  (In addition to Implicit) Two types, SPOT and SECTION