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Advanced Queuing - Oracle

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Modeling Queue Entities<br />

Consumers<br />

According to the figure, there are 3 consumers of messages, representing the total<br />

population of consumers. The figure shows that:<br />

Messages are not necessarily dequeued in the order in which they are<br />

<br />

enqueued.<br />

Messages may be enqueued without being dequeued.<br />

AQ Client-Server Communication<br />

The figure portrays the enqueuing of multiple messages by a set of producers, and<br />

the dequeuing of messages by a set of consumers. What may not be readily evident<br />

in that sketch is the notion of time and the advantages offered by <strong>Oracle</strong> AQ.<br />

Client-Server applications normally execute in a synchronous manner, with all the<br />

disadvantages of that tight coupling described earlier. Figure 7–3 demonstrates the<br />

asynchronous alternative using AQ. In this example Application B (a server)<br />

provides service to Application A (a client) using a request/response queue.<br />

Modeling and Design 7-5

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