The concept behind Advanced Queuing (also known as AQ) is fairly simple. In a normal interaction with an Oracle8i
database, the communication between a user and the database server is synchronous
when a user sends a message to the Oracle server and waits for a response from the server.
Advanced Queuing uses the capabilities of the Oracle server to implement asynchronous
communication. A user sends a message to a queue, where it waits until another user or process takes the message out of the queue.
The sender is not blocked while waiting for a response from the server, as it is with synchronous communication.
The process of communication between the sender and recipient of a message is still guaranteed. The main difference in implementation is that the delivery time is not guaranteed, because it is dependent on when a recipient retrieves a
message as well as when the message is sent.
The following SlideShow illustrates Advanced Queuing at work: