getting message: oci_execute(): ORA-00942: table or view does not exist

This is wrong CodeIgniter CI_Model has no constructor so you cannot use 

PHP Code:

parent::__construct(); 


This is how it should be, see how the class name is ucfirst uppercase it also needs to be saved that way.

PHP Code:

class Dep_models extends CI_Model
{
    private $oracle_db;

    public function __construct() //model construct function
    {
        $this->oracle_db = $this->load->database('oracle',true); // oracle db
    }

    public function getDept()
    {
        $query = $this->oracle_db->get('departments')
                      ->result();

        return $query;
    }
} 


Of course you would need to add error checking on all of your database code.
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