Change documents for the custom transaction

Question

hi,
how could we trap the changes in our custom transaction to CDHDR,CDPOS tables.
we had created the object and generated update information.
where exactly we should call our  write_document function module (generated in the object class ) in our module pool program.

Answer 1

Activate the 'Change document' checkbox for data element. You must updating some table by your program. So just check the 'Change document'  checkbox for those dataelement that you are updating in the table.
You will find the 'Change document' checkbox in the following path : dataelement-> farther element->'Change document'  checkbox.
Now, if that checkbox is checked, the CDHDR and CHPOS table will be updated whenever you do any chnge in the table.
Now you can readthe table with a date to find out whether the bable is modified.
Now performance wise it is better to use change pointer instead of change document. Change pointer also do the same functionality as the change document.
To do that go to BD52, give a message type andd all the table and fields for which you are updating through your program.
Now you can use 'Change_pointer_read' FM to read the values that are change.
Ex:
        CALL FUNCTION 'CHANGE_POINTERS_READ'
          EXPORTING
            message_type                = gc_message_type
            creation_date_high          = s_erdat-high
            creation_date_low           = s_erdat-low
            creation_time_high          = gc_time_high
            creation_time_low           = gc_time_low
            read_not_processed_pointers = 'X'
          TABLES
            change_pointers             = lt_chgptrs_tab.
gc_message_type message you have given in BD52 and you will get all the chaged element in lt_chgptrs_tab.
Now after reading the values to update the fact that you have read those values you have to call another FM.
          CALL FUNCTION 'CHANGE_POINTERS_STATUS_WRITE'
            EXPORTING
              message_type           = gc_message_type
            TABLES
              change_pointers_idents = gt_pointer_id.
          COMMIT WORK.
gt_pointer_id will have all the change pointer ids from lt_chgptrs_tab table that you have already reead.
The table for change pointer is BDCP.