1. Field exit was created with CMOD, but is not processed when calling the screen.

-  Since the field exit is not processed until PAI, an action must be triggered on the screen (Return, Save, ...).

-  Set profile parameter abap/fieldexit to YES and restart the system.

-  After activating the function module FIELD_EXIT... and the field exit, leave the transaction on whose screen the field exit is to be executed. The screen is not generated until the transaction is started.

- Do not work on different application servers since there may be some delay before the field exit is activated.

- The profile parameter must be set on all or none of the application servers.

- If the field exit is to only be active on specific screens, check whether you chose the correct program and the correct screen
      number (take care with subscreens).

- Using SE51 -> Field list, check that the screen field does have a reference to a data element. In the name of the field exit use the name of the data element and not the field name.

- After transport, field exits are marked as active but will not be processed. 
   Tip: First try deactivating the field exit once more and then afterwards, activate it again.

2. How is performance affected by setting abap/fieldexit?

- If a screen is generated and the profile parameter is set, a check is run on 2 tables (TDDIR, TDDIRS) to see whether a field exit must be generated for the respective field. In practice, the screen load is not generated until the screen is selected after an
update. The user should not notice any difference because screen generation is very fast.

3. Can you read the contents of other screen fields in the field exit?

- In principle, every field exit can store its value in the global variables of the function group (TOP) and hence make them
available to other field exits. Note here that field exits are always called and not only if an entry is made in the field or if the field is empty. In addition, it is not possible to make any assumptions about the order in which the field exits will be called in the future.

4. How does the field exit behave on step loop fields ?

- After the user has entered data, the field exit is called in PAI as often as there are visible fields in the step loop. The system
variable SY-STEPL is incremented each time. If a new value is assigned to the field, it is displayed in the module between LOOP and ENDLOOP. This module is also called once for each visible step loop line.

5. Can field exits be debugged ?

- No. Field exits must be tested separately in the ABAP/4 Development Workbench. For errors which only occur in the screen environment, it is helpful to write interesting variable to the file system using TRANSFER... . These can then be analysed there.

6. What can you do if the field contents are no longer transported to to ABAP/4.

- Check whether a value is assigned to the field OUTPUT.

7. When is the field exit called if a conversion exit is attached to the
   data element ?

- The field exit is called after the conversion exit. This means that the INPUT field receives the data in the same format as the
ABAP/4 program also receives it.

8. Although a global field exit is inactive, a function module is called which does not exist (for example FIELD_EXIT_PROGRAMM_@)

- This is an error in the kernel which no longer occurs as of 3.0C.  As a temporary measure, it is useful to assign a program and a screen which do not exist to the field exit and then activate the field exit.

9. Field exit is not visible in CMOD, although created.

- If you want to create a field exit for a data element, a function module is proposed with the name FIELD_EXIT_. This
function module must exist for the field exit to work. If you do not create this function module, but do create one with a suffix,
the data element is not displayed in CMOD.

10. Field exit is not executed although it is active.

-  Fields which do not have the 'Input field' attribute usually do not trigger a field exit. The field exit is designed to allow an
extended input check. It is therefore only called for input fields - even if they are not ready for input at runtime of the         application by LOOP AT SCREEN.
This rule does not apply, however, if the field is located within a steploop. Here the field will be always activated, even if it is
invisible.

- Field exits can only be executed for fields that are directly related tothe dictionary. If the relation is indirect, i.e. via an       ABAP declaration (  LIKE ), no field exit can be executed.

11. Field exits on check buttons do not work

-  Field exits are only intended for input fields. As check buttons count as graphical elements, you cannot install field exits on
them.

12. Field exits do not work on selection screens

Fast Links:
User Exit Tutorial
A Short Tutorial on User Exits

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