Conexão com Oracle dá erro

Caros estou tentando conectar com o Oracle 9i, estou usando Zend 1.5, mas dá a seguinte mensagem de erro:

Notice: Use of undefined constant OCI_COMMIT_ON_SUCCESS - assumed 'OCI_COMMIT_ON_SUCCESS' in C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db.php on line 247

Fatal error: Uncaught exception 'Zend_Db_Adapter_Oracle_Exception' with message 'The OCI8 extension is required for this adapter but the extension is not loaded' in C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Adapter\Oracle.php:102 Stack trace: #0 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Adapter\Abstract.php(743): Zend_Db_Adapter_Oracle->_connect() #1 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Adapter\Abstract.php(813): Zend_Db_Adapter_Abstract->quote('C_UF', NULL) #2 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Adapter\Oracle.php(299): Zend_Db_Adapter_Abstract->quoteInto('UPPER(TC.TABLE_...', 'C_UF') #3 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Table\Abstract.php(605): Zend_Db_Adapter_Oracle->describeTable('C_UF', 'SIARCOWEB') #4 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Table\Abstract.php(534): Zend_Db_Table_Abstract->_setupMetadata() #5 C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Table\Abstract.php(269): Zend_Db_Table_Abstract->_setup() #6 C:\Services\AppServ\www\SIARCOWEB\app\controllers\IndexCont in C:\Services\AppServ\www\SIARCOWEB\lib\Zend\Db\Adapter\Oracle.php on line 102

Alguém sabe como proceder para corrigir esse bug???