TYPES tt_materials TYPE STANDARD TABLE OF marc WITH DEFAULT KEY.

SELECT * UP TO 20 ROWS
INTO TABLE @DATA(materials)
FROM marc
ORDER BY matnr, pstat.

DATA duplicates TYPE tt_materials.
LOOP AT materials INTO DATA(material)
   GROUP BY ( id    = material-matnr
              status = material-pstat
              size  = GROUP SIZE )
  ASCENDING REFERENCE INTO DATA(group_ref).

  CHECK group_ref->*-size > 1.
  DATA(members) = VALUE tt_materials( FOR <status> IN GROUP group_ref ( <status> ) ).
  duplicates = VALUE tt_materials( BASE duplicates FOR member IN members ( member ) ).

ENDLOOP.