How can I update BUT050 & BUT051 tables? - abap

Question

I have the following scenario:
I am using BAPI BAPI_BUPR_RELATIONSHIP_CHANGE to change validuntildate. (BUT050-DATE_TO / BUT051-DATE_TO).
But I also need to update field BUT051-PAFKT and a custom field in BUT050 (lets call it ZZFIELD).
I do this by updating BUT050 / BUT051 from internal tables.
At the end, if I write COMMIT WORK or call FM BAPI_TRANSACTION_COMMIT, only the fields from BAPI_BUPR_RELATIONSHIP_CHANGE will be updated. If I do not write anything at the end, only the field from UPDATE FROM TABLE will be updated.
How can I update all my fields?
Are there any BAPI that can allow me to modify BUT051-PAFKT and custom fields from BUT050 ?
Sample code for testing:
DATA: lt_return TYPE bapiret2_t,
lv_kunnr TYPE kunnr VALUE '111',
lv_partner TYPE bu_partner VALUE '222',
lv_rel_cat TYPE bu_reltyp VALUE 'BUR001',
lv_new_date TYPE sy-datum VALUE '20300101',
lt_but051 TYPE TABLE OF but051.
CALL FUNCTION 'BAPI_BUPR_RELATIONSHIP_CHANGE'
EXPORTING
businesspartner1 = lv_kunnr
businesspartner2 = lv_partner
relationshipcategory = lv_rel_cat
validfromdate = sy-datum
validuntildate = sy-datum
validuntildatenew = lv_new_date
datetox = abap_true
TABLES
RETURN = lt_return.
SELECT *
FROM but051
INTO TABLE lt_but051
WHERE partner1 = lv_kunnr
AND partner2 = lv_partner
AND reltyp = lv_rel_cat.
LOOP AT lt_but051 ASSIGNING FIELD-SYMBOL(<ls_but051>).
<ls_but051>-pafkt = '0003'.
ENDLOOP.
UPDATE but051 FROM TABLE lt_but051.
COMMIT WORK.

Answer 1

Try this (or its wrapper BAPI_BUPR_CONTP_CHANGE):
DATA: ls_person TYPE bapibus1006_central_person.
DATA: ls_person_x TYPE bapibus1006_central_person_x.
DATA: ls_central TYPE bapibus1006_central.
DATA: ls_central_x TYPE bapibus1006_central_x.
DATA: lt_return TYPE bapiret2_t.
is_data-function = '0001'. "<-- your PAFKT
is_data_x-function = abap_true.
* changes of the central data
CALL FUNCTION 'BUPR_CONTP_CHANGE'
EXPORTING
iv_partner = is_data-partner1
* IV_PARTNER_GUID =
iv_contactperson = is_data-partner2
* IV_CONTACTPERSON_GUID =
* IV_DATE_FROM =
* IV_DATE_TO =
* IV_DEFAULTRELATIONSHIP =
* IV_DEFAULTRELATIONSHIP_X =
is_data = is_data-data
is_data_x = is_data_x-central
* IV_TESTRUN = ' '
TABLES
et_return = lt_return.
CALL FUNCTION 'BAPI_TRANSACTION_COMMIT'
EXPORTING
WAIT = abap_true.
Also check my answer about updating relations and the corresponding note.
Regarding the custom field in BUT050, you can't just add a new field and update it, you need to change the BOL model.