Hi guru's i am learning ,i am learning user exists plz help me

Question

hi guru's i  am learning ,i am learning user exists , i don't know anything about that plz help me lie realtime oriented

Answer 1

Hi
USER EXIT
EXIT s are nothing but the R/3 Enhancements which allows you to add your own functionality to SAP’s standard business applications without having to modify the original applications.
Purpose
To introduce the techniques of enhancement in standard SAP system. SAP creates customer exits for specific programs, screens, and menus within standard R/3 applications. These exits do not contain any functionality. Instead, the customer exits act as hooks. You can hang your own add-on functionality onto these hooks.
Use
They do not affect standard SAP source code.
When you add new functionality to your SAP System using SAP’s exits, you do not alter the source code of standard SAP programs in any way. The code and screens you create are encapsulated as separate objects. These customer objects are linked to standard applications, but exist separately from SAP’s standard software package.
They do not affect software updates.
When you add new functionality to your SAP System using SAP’s exits, your objects (called customer objects) must adhere to strict naming conventions. When it comes time to upgrade a to a new software release, customer objects’ names ensure that they will not be affected by any changes or new additions to the standard software package.
Challenges
Customer exits are not available for all programs and screens found in the SAP System.
Modifications
Any change made to an SAP object in a customer system is called a modification. Customers usually modify their systems for one of two reasons. Either they make changes to the SAP standard in order to adjust the R/3 System to their specific business needs (actual modifications), or they alter individual SAP objects in order to correct an error (as recommended in an SAP error note).
You should only modify the SAP standard if the modifications you want to make are absolutely necessary for optimizing work flow in your company. Be aware that good background knowledge of application structure and flow are important prerequisites for deciding what kind of modifications to make and how these modifications should be designed.
need
ABAP DICTIONARY
Table Enhancements: There are two ways that you can add additional fields to tables without modifying your system.
Append Structures:
Append structures allow you to enhance tables by adding fields to them that are not part of the standard. With append structures, customers can add their own fields to any table or structure they want.
Append structures are created for use with a specific table. However, a table can have multiple append structures assigned to it.
Customizing Includes:
If customers know in advance that one of the tables or structures delivered to them by SAP needs to have customer-specific fields added to it, an SAP application developer can include these fields in the table using a Customizing include statement.
The same Customizing include can be used in multiple tables or structures. This provides for consistency in these tables and structures whenever the itself include is altered.
Append structures allow you to attach fields to a table without actually having to modify the table itself.
Append structures may only be assigned to a single table. A table may, however, have several append structures attached to it. Whenever a table is activated, the system searches for all active append structures for that table and attaches them to the table. If an append structure is created or changed and then activated, the table it is assigned to is also activated, and all of the changes made to the append structure take effect in the table as well.
You can use append structures in ABAP programs just as you would any other structure.
Note: When you copy tables that have append structures attached to them, the fields that were found in the append structure of the original table become part of the actual body of the target table.
Some of the tables and structures delivered with the R/3 standard contain special include statements calling Customizing includes. These are often inserted in those standard tables that need to have customer-specific fields added to them.
In contrast to append structures, Customizing includes can be inserted into more than one table. This provides for data consistency throughout the tables and structures affected whenever the include is altered.
Customizing include programs are part of the customer namespace: all of their names begin with 'CI_'. This naming convention guarantees that nonexistent Customizing includes do not lead to errors. No code for Customizing includes is delivered with the R/3 standard.
You create Customizing includes using special Customizing transactions. Some are already part of SAP enhancements and can be created by using project management (see the unit on 'Enhancements using Customer Exits').
The Customizing include field names must lie in the customer namespace just like field names in append structures. These names must all begin with either 'YY' or 'ZZ'.
When adding the fields of a Customizing include to your database, adhere to same rules you would with append structures.
ABAP DICTIONARY
Field Exits:
Field exits take you from a screen field with a data element reference to a function module. Field exits can be either global or local.
Field exit function modules adhere to the following naming convention:
prefix: FIELD_EXIT_
name: <data element name>_
suffix (optional): 0 to 9, A to Z
Text Enhancements:
Possible text enhancements include customer keywords and customer documentation of data elements.
Text enhancements differ from other application enhancements in that they take effect globally in all related SAP applications after activation (global enhancements).
Customer Exits
Function Module Exits
Menu Exits
Screen Exits
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 pull down 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.
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.
SAP creates menu exits by defining special menu items in the Menu Painter. These special entries have function codes that begin with "+" (a plus sign). You specify the menu item’s text when activating the item in an add-on project.
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.
Exits are basically the hooks whcih SAP has provided to add your own code. There are two types of Exits:
1. Customer exits: Implemented as Function Modules within z includes. Anybody can change it and no access key is required.
2. User Exit: Implemented as subroutines within includes (any include except y or z includes). You need access for the specific include and then you can any subroutine (user exit) within that Include.
BADIs are the enhanced version of user exits where the same logic is implemented via classes and object (OOP)
Enchancement point is the latest once introduces with ECC6.0 . Not very sure about that but you can change it without any access key.
Please go through the following link which will help you understand the exits in a much better way:
http://help.sap.com/saphelp_nw04/helpdata/en/bf/ec07a25db911d295ae0000e82de14a/content.htm
http://www.sap-img.com/abap/what-is-the-difference-between-smod-and-cmod.htm
http://sap.niraj.tripod.com/id21.html
http://help.sap.com/saphelp_nw04/helpdata/en/c8/1975cc43b111d1896f0000e8322d00/frameset.htm
http://www.sap-img.com/ab038.htm
User Exits.
http://www.erpgenie.com/sap/abap/code/abap26.htm
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sapgenie.com/abap/code/abap26.htm
http://www.sap-img.com/abap/what-is-user-exits.htm
http://wiki.ittoolbox.com/index.php/HOWTO:Implement_a_screen_exit_to_a_standard_SAP_transaction
http://www.easymarketplace.de/userexit.php
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sappoint.com/abap/userexit.pdfUser-Exit
customer exits
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/f1a7e790-0201-0010-0a8d-f08a4662562d
Menu Exit.
http://www.sappoint.com/abap/spmp.pdf
http://www.sappoint.com/abap/userexit.pdf
http://www.sapdevelopment.co.uk/enhance/mod_sapmenu.htm
http://www.sapdevelopment.co.uk/enhance/enhancehome.htm
USER EXIT
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sapgenie.com/abap/code/abap26.htm
http://www.sap-img.com/abap/what-is-user-exits.htm
http://wiki.ittoolbox.com/index.php/HOWTO:Implement_a_screen_exit_to_a_standard_SAP_transaction
http://www.easymarketplace.de/userexit.php
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sappoint.com/abap/userexit.pdfUser-Exit
http://www.sap-img.com/ab038.htm
http://help.sap.com/saphelp_46c/helpdata/en/64/72369adc56d11195100060b03c6b76/frameset.htm
http://www.sap-img.com/abap/a-short-tutorial-on-user-exits.htm
http://www.sap-img.com/abap/what-is-user-exits.htm
http://expertanswercenter.techtarget.com/eac/knowledgebaseAnswer/0,295199,sid63_gci982756,00.html