Updation of Primary Key in HR Table(PA2001)

Question

Can anyone please tell me how to update a primary key field in HR Tables (PA2001 and PA2002).
I need to update <b>sprps</b> field in both the tables. I used HR_Infotype_Operation function module, but still it is not updating the field.
Pls find the following code snippet for the table PA2001 and let me know if any discrepancies :
TABLES: pa2001.
DATA: it_pa2001 TYPE TABLE OF pa2001,
      wa_pa2001 LIKE LINE OF it_pa2001,
DATA: date TYPE d.
date = sy-datum - 100.
SELECT pernr sprps begda endda FROM PA2001 INTO CORRESPONDING FIELDS OF TABLE it_pa2001
  WHERE begda BETWEEN date and sy-datum.
WRITE:/.
WRITE:/ 'PA 2001 Records'.
if sy-subrc <> 0.
  WRITE:/ 'No Data Exists'.
else.
LOOP AT it_pa2001 INTO wa_pa2001.
WRITE:/ wa_pa2001-pernr, wa_pa2001-sprps, wa_pa2001-begda, wa_pa2001-endda.
ENDLOOP.
endif.
LOOP AT it_pa2001 INTO wa_pa2001.
wa_pa2001-sprps = 'X'.
                                 CALL FUNCTION 'HR_INFOTYPE_OPERATION'
                                   EXPORTING
                                     infty                  = '2001'
                                     number                 = wa_pa2001-pernr
                                   SUBTYPE                =
                                   OBJECTID               =
                                   LOCKINDICATOR          =
                                   VALIDITYEND            =
                                   VALIDITYBEGIN          =
                                   RECORDNUMBER           =
                                     record                 = wa_pa2001
                                     operation              = 'MOD'
                                   TCLAS                  = 'A'
                                   DIALOG_MODE            = '0'
                                   NOCOMMIT               =
                                   VIEW_IDENTIFIER        =
                                   SECONDARY_RECORD       =
                                 IMPORTING
                                   RETURN                 =
                                   KEY                    =
ENDLOOP.
if sy-subrc = 0.
write:/ 'SY-subrc is zero'.
write:/ ' Rows modified = ', sy-dbcnt.
else.
write:/ 'No Record(s) updated'.
endif.
commit work.
WRITE: / 'Updated Records in the Internal Table IT_PA2001'.
SELECT pernr sprps begda endda FROM PA2001 INTO CORRESPONDING FIELDS OF TABLE it_pa2001
  WHERE begda BETWEEN date AND sy-datum..
LOOP AT it_pa2001 INTO wa_pa2001.
WRITE:/ wa_pa2001-pernr, wa_pa2001-sprps, wa_pa2001-begda, wa_pa2001-endda.
ENDLOOP.

Answer 1

Thanks Kiran.
But I need to change this field as we need to lock the records, as soon as the employee fills his/her time sheets which will be sent for HR Payroll, later on.
When I am updating directly the field the database table PA2001, its not updating but for table PA2002, only few records are being updated.
Is there any other alternative for this problem?
Pls reply.
Thanks,
Harish