Advanced Queuing - Oracle

Modeling Queue Entities
Message Propagation
notification for message delivery. Application C registers for messages on the
queue. When messages arrive, application C is notified and can dequeue the
messages.
Fanning-Out of Messages
In AQ, message recipients can be either consumers or other queues. If the message
recipient is a queue, the actual recipients are determined by the subscribers to the
queue (which may in turn be other queues). Thus it is possible to fan-out messages
to a large number of recipients without requiring them all to dequeue messages
from a single queue.
For example, a queue, Source, may have as its subscribers queues dispatch1@dest1
and dispatch2@dest2. Queue dispatch1@dest1 may in turn have as its subscribers the
queues outerreach1@dest3 and outerreach2@dest4, while queue dispatch2@dest2 has as
subscribers the queue outerreach3@dest21 and outerreach4@dest4. In this way,
messages enqueued in Source will be propagated to all the subscribers of four
different queues.
Compositing (Funneling)
You can also combine messages from different queues into a single queue,
sometimes described as compositing. For example, if queue composite@endpoint is a
subscriber to both funnel1@source1 and funnel2@source2, then the subscribers to
composite@endpoint can get all messages enqueued in those queues as well as
messages enqueued directly to itself.
Propagation and Advanced Queuing
Figure 7–10 illustrates applications on different databases communicating using
AQ. Each application has an inbox and an outbox for handling incoming and
outgoing messages. An application enqueues a message into its outbox irrespective
of whether the message is sent locally (on the same node) or remotely (on a
different node ). An application dequeues messages from its inbox irrespective of
7-14 Oracle9i Application Developer’s Guide - Advanced Queuing