identifier 'SETUP_SESSION' must be declared

I use a version of the module

; Information added by drupal.org packaging script on 2013-05-25
version = "7.x-1.12+4-dev"
core = "7.x"
project = "oracle"
datestamp = "1369449108"

when i connect to external database i get this error

ORA-06550: line 1, column 16:
PLS-00201: identifier 'SETUP_SESSION' must be declared
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored

it is obtained very often
I looked at the code, it happend in this place

$stmt= parent::prepare("begin ? := setup_session; end;");
$stmt->bindParam(1, $this->max_varchar2_bind_size, PDO::PARAM_INT|PDO::PARAM_INPUT_OUTPUT, 32);

file: /includes/database/oracle/database.inc
line: 122

how can i escape this error?