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RSMODPRF - Field Exits for Data Elements

RSMODPRF - Field Exits for Data Elements

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Description

Maintenance transaction for creating and activating field exits

As part of the extension concept, SAP allows you to install a field exit for each screen field. Similar to the conversion exit, the system branches at the field exit at DCI (DATA COMMUNICATIONS INPUT) to a function module, if the field is an input field and a function code was triggered. The function module must adhere to the following naming convention:

  • Prefix: FIELD_EXIT_
  • Infix:
  • Suffix: _0 to _9 (optional), _A to _Z

The interface is automatically generated during the creation of the function module, and has 2 parameters:

  • Import parameter: INPUT
  • Export parameter: OUTPUT

After a function code has been triggered the contents of the field are made available to the FB via the "INPUT" import parameter. You can edit this and, when changed, make it available to the ABAP/4 processor in "OUTPUT". The input field contents are usually passed on: you can simply write OUTPUT = INPUT.

If, e.g., you have activated the field exit for the data element 'PROGRAM', then the fields of all the screens, which refer to the data element 'PROGRAM', branch to the function module FIELD_EXIT_PROGRAM. This includes the field 'Program' of the initial screen SAPMS38M0100 in transaction SE38, for example.
If you do not want the function module to be accessed from all screens, assign particular screens to the data element PROGRAM. By allocating an exit number, it is also possible to branch to other function modules with the corresponding suffix _0 ... _Z.

Example: You have assigned screen SAPMS38M0100 and exit number 5 to data element 'PROGRAM'. The corresponding field on SAPMS38M0100 branches to FIELD_EXIT_PROGRAMM_5.

As soon as you activate an exit, the corresponding screens are invalidated.

Note: Field exits are only taken into account during screen generation if the parameter abap/fieldexit = 'YES' is set in the system profile.

Requirements

Set the profile parameter abap/fieldexit = 'YES' before system start.

Limitations

The following ABAP statements are not allowed in the function modules of field exits:

BREAK-POINT,
CALL SCREEN, CALL DIALOG, CALL TRANSACTION, SUBMIT,
COMMIT WORK, ROLLBACK WORK,
COMMUNICATION RECEIVE,
EXIT FROM STEP-LOOP,
MESSAGE I, MESSAGE W.

Note:

  • Field exits cannot be edited with the debugger.
  • You should not use any external Performs in field exits. The ABAP processor shares the table work areas of externally called programs with those of the first caller. This could lead to errors at field exits that can hardly be analyzed, as field exits are sometimes slipped into the flow of the program at unforeseen events.

Questions and answers on field exits

1. A field exit was created with the CMOD and activated, but it does not get executed when the screen is called.

  • Since the field exit is not executed until DCI, some action must occur in the screen (e.g. press Return, saving....).
  • Set the abap/fieldexit profile parameter to YES and start the system again.
  • After the FIELD_EXIT... function module has been activated and the field exit has been activated, the transaction in whose screen the field exit is to be executed must be terminated. The screen is not generated until it is called.
  • Do not work on different application servers, otherwise there may be a delay before the field exit becomes active.
  • The profile parameter must be set either on all application servers or on none.
  • If the field exit is to be active in certain screens only, then you should check whether you have selected the correct program and the correct screen number (Careful with SUBSCREENS !).
  • Use SE51, field list, to ensure that the screen field really does have a DDIC reference! Do not rely on the F1 information for the field!

2. How does setting abap/fieldexit affect the performance?

  • If a screen is generated and the profile parameter is set, then the system checks in 2 tables (TDDIR, TDDIRS) to see whether a field exit has to be generated for the field. In practice the screen load after a Put is not generated until the screen is called. The user will not experience a noticeable delay, since screen generation is extremely fast.

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

  • In principle all fields can be copied to global variables in the TOP or the function group. However, since the order in which the field exits are called is not guaranteed, this possibility should not be used.

4. How does the field exit work in step-loop fields?

  • After data input to DCI the field exit will be called as many times as fields are visible on the step-loop. The SY-STEPL system variable is incremented each time. If a new value is assigned to be field, then it will be visible in the module between LOOP. ENDLOOP. This module will also be called as many times as there are visible step-loop lines.

5. Can field exits be debugged?

  • No. Field exits have to be tested in isolation in the development environment. To analyze problems that occur only in the screen environment, the relevant variables can be written to the file system using TRANSFER... and can be analyzed there.

6. What should one do if the field contents are not getting transported to ABAP/4?

  • Check whether you have assigned a value to the OUTPUT field.

7. When does the field exit get called in the case that there is a conversion exit attached to the data element?

  • The field exit will be called after the conversion exit. This means that the INPUT field contains the data in the same form as that in which the ABAP/4 program also gets them.





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