function myCiInser(){
... Here is my query ...
//$data: this var is result query that is true
if($data){
    $this -> session -> set_flashdata('message', 'Your information was successfully updated.');
    redirect('url/myurl');
            }
}

<?php
$message = $this->session->flashdata('message');
    if($message){
        echo '<div id="error_text">' . $message . '</div>';
    }
//I test this : "echo $message;" but don't give output
?>

$this->session->keep_flashdata('message');

redirect('url/myurl','refresh');

$this->session->set_flashdata('sessionkey', 'Value');

redirect("admin/signup");

$this->session->flashdata('sessionkey');

$config['sess_match_ip'] = FALSE;
$config['sess_match_useragent'] = FALSE;

if (0)//Assume this condition is false

  {
    $this->load->view('error_page');
    // Generate validation error
  }

 else
  {
     //Show success message
     $data = array(
     'message' => 'My message'
     );
     $this->session->set_flashdata($data);
     $this->session->keep_flashdata($data);
     echo $this->session->flashdata('message');
     //echo var_dump($this->session);
     //redirect(base_url().'success_page');
    }

$this->session->flashdata('message');

print_r($this->session->flashdata('message'));