Queue Models

Oracle Streams Advance Queuing (AQ) supports two queue models—point-to-point and publish/subscribe. A point-to-point queue is also known as a single-consumer queue. The message producer and consumer use a common queue to exchange messages. The producer enqueues a message to the queue and the consumer dequeues it. The message in a point-to-point or single-consumer queue can be dequeued only once from the queue.

Publish/subscribe queues are also known as multiconsumer queues because the message is intended to reach multiple targets. In other words, this type of queue is used to broadcast a message to multiple clients. The message producer enqueues the message to the queue. The message stays in the queue until it is dequeued by each message consumer. The applications or consumers that want to receive the message have to subscribe to the queue to receive the message. Oracle Streams AQ keeps track of the subscribers and notifies each one when the message is ready in the queue to be dequeued. These queues support rules for delivery to consumers.