Unlike transactions and executable programs, dialog modules do not start a new SAP LUW. Calls to update-task function modules from a dialog module use the same update key as the ones in the calling program. The result is that calls to update function modules from a dialog module are executed only if a COMMIT WORK statement occurs in the calling program.
If you place a COMMIT WORK in a dialog module, it does commit changes to the database (for example, with UPDATE).However, it does not start the update task. The function modules are not actually executed until a COMMIT WORK statement occurs in the calling program.
If you use dialog modules, try to avoid including calls to update function modules in subroutines called with PERFORM ON COMMIT. In general, any occurrence of PERFORM ON COMMIT(with or without update-task function calls) in a dialog module can be problematic.
This is because dialog modules have their own roll area, which disappears when the module finishes. Consequently, all local data (including data used for parameter values when calling an update function module) disappears as soon as the commit in the main program is reached.
If you must use this method in a dialog module (i.e. include the call to an update-task function in a subroutine), you must ensure that the values of the actual parameters still exist when the update-task function actually runs. To do this, you can store the required values with EXPORT TO MEMORY and then import them back into the main program (IMPORT FROM MEMORY) before the COMMIT WORK statement.