What's the purpose of using PACKAGE SIZE in select statement? SAP ABAP INTERVIEW Questions

Package size can be used if you for example only want to finish processing a limited amount of data at a time due to lack of memory.

The example below read 50 records at a time from VBAK into an internal table, and selects the corresponding entries from vbap into an internal table. Then the two internal tables can be processed, and the next 50 records from VBAk can be read. Remember to reinitialize tha tables before the next read.

REPORT z_test.

TYPES:
BEGIN OF t_vbak,
vbeln LIKE vbak-vbeln,
erdat LIKE vbak-erdat,
END OF t_vbak,

BEGIN OF t_vbap,
posnr LIKE vbap-posnr,
matnr LIKE vbap-matnr,
meins LIKE vbap-meins,
END OF t_vbap,

BEGIN OF t_report,
vbeln LIKE vbak-vbeln,
erdat LIKE vbak-erdat,
posnr LIKE vbap-posnr,
matnr LIKE vbap-matnr,
meins LIKE vbap-meins,
END OF t_report.

DATA:
li_vbak TYPE t_vbak OCCURS 0,
l_vbak TYPE t_vbak,
li_vbap TYPE t_vbap OCCURS 0,
l_vbap TYPE t_vbap,
li_report TYPE t_report OCCURS 0,
l_report TYPE t_report.

START-OF-SELECTION.
SELECT vbeln erdat
FROM vbak
INTO TABLE li_vbak PACKAGE SIZE 50.
SELECT posnr matnr meins
FROM vbap
INTO TABLE li_vbap
FOR ALL ENTRIES IN li_vbak
WHERE vbeln = li_vbak-vbeln.
IF sy-subrc = 0.
* Now you have the two internal tables li_vbak and li_vbap filled
* with data.
* Do something with the data - remember to reinitialize internal
* tables
ENDIF.
ENDSELECT.

*-- End of Program