Cannot connect to oracle database

[eluser]mhel_dc[/eluser]
I'm using CI 1.7.2 connecting to oracle 10g

Code:

$active_group  = "abora";
$active_record = TRUE;

$db['abora']['hostname'] = "(DESCRIPTION =(ADDRESS_LIST =(ADDRESS = (PROTOCOL = TCP)(HOST = oraserver.domain.com)(PORT = 1522)))(CONNECT_DATA =(SERVICE_NAME = orasid)))";
$db['abora']['username'] = "orauser";
$db['abora']['password'] = "orapass";
$db['abora']['database'] = "";
$db['abora']['dbdriver'] = "oci8";
$db['abora']['dbprefix'] = "";

A PHP Error was encountered

Severity: Notice

Message: Use of undefined constant OCI_COMMIT_ON_SUCCESS - assumed 'OCI_COMMIT_ON_SUCCESS'

Filename: database/DB.php

Line Number: 133

If this is no bug... what else can I do?