A messaging gateway is also available for propagation to other systems,
such as MQSeries and TIBCO.
Publish-and-subscribe capabilities
Oracle8i Enterprise Edition introduced publish-and-subscribe capabilities to
Advanced Queuing. As illustrated in Figure 13-3, a publisher puts a message onto a
queue, while a subscriber receives messages from a queue. The publisher and subscriber
interact separately with the queue, and neither party needs to know of the
existence of the other. Publishers decide when, how, and what to publish, while subscribers
express an interest. Messages can be published and subscribed to using the
subject name or content (through filtering rules). Asynchronous notification is
enabled when subscribers register callback functions.
You can use Advanced Queuing and its publish-and-subscribe features for additional
notification of database events that, in turn, improve the management of the
Moving Data Between Distributed Systems | 315
database or business applications. Database events such as DML (inserts, updates,
deletions) and system events (startup, shutdown, and so on) can be published and
subscribed to.
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