Cannot purge Alert notifications from wf_notification_out

Hi

I want to purge all the old alerts in READY  and Processed state.

follow the steps in the document,but the record still exist,could you tell me how to purge them?
How to Remove Unwanted Messages from Mailer's Queue without Rebuilding the Queue? (https://mosemp.us.oracle.com/epmos/faces/ui/km/DocumentDisplay.jspx?id=759747.1Doc ID 759747.1)

declare
q_version varchar2(200);
event sys.aq$_jms_text_message;
dequeue_options dbms_aq.dequeue_options_t;
message_properties dbms_aq.message_properties_t;
TYPE msgIDTAB is table of raw(16) index by binary_integer;
msg_id msgIDTAB;
dq_msg_id raw(16);