高手啊statement.registerOutParameter

高手求助啊！！statement.registerOutParameter
java statement.registerOutParameter(5, java.sql.Types.VARCHAR)返回值长度限制

try {
        // 初始化连接对象
        Class.forName("com.sybase.jdbc2.jdbc.SybDriver");
        cn = DriverManager.getConnection("jdbc:sybase:Tds:172.16.16.191:8000/gfc", "readuser", "123456");

        cs = cn.prepareCall("{call dbo.test_gds(?,?,?,?)}"); // 获得声明对象

        cs.registerOutParameter(3,java.sql.Types.VARCHAR);
        cs.registerOutParameter(4,java.sql.Types.VARCHAR);
        cs.setString(1,"100001");
        cs.setString(2,"100005");
        cs.execute(); 
        
        System.out.print(cs.getString(3) + " ");
        System.out.println(cs.getString(4));
              

       if (cs != null)
            cs.close(); // 关闭声明
        if (cn != null)
            cn.close(); // 关闭连接
    } jdbc sybase
[解决办法]
registerOutParameter(5, java.sql.Types.VARCHAR)哪里来的第五个参数啊