The Broker places documents that match a client's subscription in the client's queue. Each client has one queue, which is part of its client state object. A document remains in the queue until the client retrieves it (and acknowledges that it has retrieved the document successfully) or until the document expires. To reduce memory usage, volatile documents that have expired can be proactively deleted at regular intervals, based on the size of the queue, from the client queues and forward queues before the client tries to retrieve them.

When the Broker queues a document for a client, it does not actually place a copy of the document in the queue. The Broker maintains only one copy of a document instance. Queues belonging to the subscribers of that document's type contain pointers to that instance.

You can use the Broker user interface to view the list of documents in a client queue and to examine the content of the documents themselves. You can also use the Broker user interface to delete documents from a queue, move documents from one queue to another, and change the order of the documents in a queue.

For information about managing queues, see Managing Forwarding Queues.