void printHeader(String header) {
        w.println("@T, \"" + header + "\"");
        w.println(" " + DataIO.KEY_CREATED_AT + ", \"" + new Date() + "\"");
        w.println(" " + DataIO.DATE_FORMAT + ", " + dfmt.toPattern());
        String dig = System.getProperty("oms3.digest");
        if (dig != null) {
            w.println(" " + DataIO.KEY_DIGEST + "," + dig);
        }
        w.print("@H");
        for (V v : vars) {
            w.print(", " + v.token());
        }
        w.println();
        w.print(" " + DataIO.KEY_TYPE);
        for (V v : vars) {
            w.print(", " + v.type());
        }
        w.println();
        printHeader = false;
    }