not able to select single entry vbeln from VBAK.

hi Gurus,

below is my ode and i am not able to select single entry from vbak table , in debugging i have seen that the select query is giving sy-subrc vaqlue as 4.

Please help.

LOOP AT it_datatab into wa_datatab.

  clear v_vbeln.

*select single vbeln from vbak into v_vbeln where vbeln eq wa_datatab-vbeln.

  select single vbeln into v_vbeln from vbak where vbeln eq wa_datatab-vbeln.

  IF sy-subrc EQ 0 and wa_datatab-vbeln = v_vbeln.

    vbkd-bstdk = wa_datatab-aft_bstdk.

*    modify vbkd from wa_datatab. "transporting bstdk.

*    update vbkd from table wa_datatab.



  ENDIF.

ENDLOOP.