我有以下informix过程

CREATE FUNCTION selectSollmandant(INOUT sollmandat SOLLMANDAT_ROW, inkassodatum INT8) RETURNING SMALLINT
DEFINE ret SMALLINT;
LET ret = 0;
trace "Entering select sollmandat " || sollmandat.vers_schein_nr;

PREPARE sollStmt FROM "SELECT s::SOLLMANDAT_ROW FROM  sollmandat s WHERE vers_schein_nr = ? ORDER BY lfdnr desc";

DECLARE _sollmCsr CURSOR FOR sollStmt;
IF SQLCODE != 0 THEN
    CALL print_to_proto("DECLARE letztZahlCsr " || SQLCODE);
    RETURN 0;
END IF;

TRACE "log ===========  1";
OPEN _sollmCsr USING sollmandat.vers_schein_nr;
TRACE "log ===========  2" || SQLCODE;

IF SQLCODE != 0 THEN
    TRACE "log ===========  3" || SQLCODE;  
    CALL print_to_proto("OPEN sollmandat " || SQLCODE);
    RETURN 0;
END IF;
TRACE "sollmandant iban is ===========  4" || SQLCODE;  
WHILE (1=1) LOOP .... end loop and return...

你能帮帮我吗?我不知道我错过了什么。