What is the result ? Why the double quotes ? Are you trying to concatenate the values (situation1) of i_etq etcetera, or the literals 'i_etq' (situation 2)
(situation1)
And concerning those fields you are concatenating: Do you know how long they are DEFINED in data declaration, maybe the spaces that are not filled are concatenated as well.
CONDENSE: i_etq, i_pidi, pmat-low, i_pnet NO-GAPS.
concatenate i_etq ',' i_pidi ',' pmat-low ',' i_pnet into i_linea-linea.
(situation 2)
i_linea-linea = 'i_etq , i_pidi , pmat-low , i_pnet '.