Notification on a multiconsumer queue

Question

I have created a multiconsumer queue. The intention is to have multiple instances of my applications receive updates whenever
the table is updated.
The trigger is defined as such
CREATE OR REPLACE TRIGGER CHANGE_HISTORY_TRIGGER AFTER INSERT ON VALUE_CHANGE_HISTORY
FOR EACH ROW
DECLARE
queueopts DBMS_AQ.ENQUEUE_OPTIONS_T;
msgprops DBMS_AQ.MESSAGE_PROPERTIES_T;
msgid RAW(16);
Triggered VARCHAR2(255);
my_msg Change_History_Trigger_Data;
BEGIN
SELECT LPath INTO Triggered FROM LP WHERE ID = :new.ID;
my_msg := Change_History_Trigger_Data(Triggered);
DBMS_AQ.ENQUEUE ('History_Queue',
queueopts,
msgprops,
my_msg,
msgid);
END CHANGE_HISTORY_TRIGGER;
In my application, I create an occi::aq::subscription object as follow
m_pAQSubscription = new oracle::occi::aq::Subscription(m_pEnvironment);
m_pAQSubscription->setSubscriptionNamespace(oracle::occi::aq::Subscription::NS_AQ);
m_pAQSubscription->setProtocol(oracle::occi::aq::Subscription::PROTO_CBK);
m_pAQSubscription->setCallbackContext((void *)this);
m_pAQSubscription->setSubscriptionName("History_Queue:Application_Name_1");
m_pAQSubscription->setPresentation(oracle::occi::aq::Subscription::PRES_DEFAULT);
m_pAQSubscription->setNotifyCallback(&COracleDB::ChangeHistoryCallback); m_pEnvironment->enableSubscription(*m_pAQSubscription); std::vector<oracle::occi::aq::Subscription> vSubscriptionList;
vSubscriptionList.push_back(*m_pAQSubscription);
m_pAQConn->registerSubscriptions(vSubscriptionList);
However, I keep getting ORA-24033 error whenever VALUE_CHANGE_HISTORY table is updated.
Is there anything missing in my code?
I've tried creating an Agent in the script. E.g.
recipients(1) := sys.aq$_agent('anydata_subscriber', NULL, NULL);
msgprops.recipient_list :=recipients;
and modified the following in my code;
m_pAQSubscription->setSubscriptionName("anydata_subscriber");
This works fine, but does that mean that each application instance can use the same agent, or do I need to create a
new agent with each instance?

Answer 1

Following is oracle description , hence separate NEW agents are required.
Cause: An enqueue was performed on a queue that has been set up for
multiple dequeuers but there were neither explicit recipients
specified in the call nor were any queue subscribers determined
to be recipients for this message.
Action: Either pass a list of recipients in the enqueue call or add
subscribers to the queue for receiving this message.