you use your own tool rather than
Enterprise Manager to display alerts, you must subscribe to the ALERT_QUE, read the
ALERT_QUE, and display an alert notification after setting the threshold levels for an
alert. To create an agent and subscribe the agent to the ALERT_QUE, use the
CREATE_AQ_AGENT and ADD_SUBSCRIBER procedures of the DBMS_AQADM package.
Next you must associate a database user with the subscribing agent, because only a
user associated with the subscribing agent can access queued messages in the secure
ALERT_QUE. You must also assign the enqueue privilege to the user. Use the
ENABLE_DB_ACCESS and GRANT_QUEUE_PRIVILEGE procedures of the
DBMS_AQADM package.

今天在看到这段话想起当时试验这个办法，dequeue时死活就是报错，先记下，有时间再试验一下。