multiple databases connectivity

I have the following code in model to connect to another database.

PHP Code:

        $db_name = $this->session->userdata('db_name');
        $this->anotherDb = $this->load->database($db_name, TRUE); 


but if I try to query in another model using the anoterDb using the following:

PHP Code:

        $query=$this->anotherDb->query("SELECT fieldValue
                                 FROM settings
                                 WHERE fieldName ="."'".$fieldName."'"
                                 )->row_array();
                      $fieldValue = $query['fieldValue']; 


error:

Message: Undefined property: Users::$anotherDb

to remove this error I need to reconnect to above database "anotherDb" in every model.
How can I solve this?


How can I make some global variable to be used in every model?