DEFINE TEMP-TABLE tt NO-UNDO
    FIELD a AS CHARACTER.

CREATE tt.
tt.a = "characters":L30.

DEF VAR res AS LONGCHAR NO-UNDO.
TEMP-TABLE tt:HANDLE:WRITE-JSON(STRING(Progress.Reflect.DataType:LONGCHAR), res, TRUE).
COPY-LOB FROM res TO FILE "output.json".