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Sun ONE Message Queue 3.5 Administrator's Guide


This glossary provides information about terms and concepts you might encounter while using Sun™ ONE Message Queue (MQ).

administered objects     A pre-configured MQ object—a connection factory or a destination—created by an administrator for use by one or more JMS clients.

The use of administered objects allows JMS clients to be provider-independent; that is, it isolates them from the proprietary aspects of a provider. These objects are placed in a JNDI name space by an administrator and are accessed by JMS clients using JNDI lookups.

asynchronous communication     A mode of communication in which the sender of a message need not wait for the sending method to return before it continues with other work.

authorization     The process by which a message service determines whether a user can access message service resources, such as connection services or destinations.

broker     The MQ entity that manages message routing, delivery, persistence, security, and logging, and which provides an interface that allows an administrator to monitor and tune performance and resource use.

client     An application (or software component) that interacts with other clients using a message service to exchange messages.

client identifier     An identifier that associates a connection and its objects with a state maintained by the MQ message server on behalf of the client.

client runtime     See MQ client runtime.

cluster     Two or more interconnected brokers that work in tandem to provide messaging services.

configuration file     One or more text files containing MQ settings that are used to configure a broker. The properties are instance-specific or cluster-related.

connection     1) An active connection to an MQ message server. This can be a queue connection or a topic connection. 2) A factory for sessions that use the connection underlying MQ message server for producing and consuming messages.

connection factory     The administered object the client uses to create a connection to MQ message server. This can be a QueueConnectionFactory object or a TopicConnectionFactory object.

consume     The receipt of a message taken from a destination by a message consumer.

consumer     An object (MessageConsumer) created by a session that is used for receiving messages from a destination. In the point-to-point delivery model, the consumer is a receiver or browser (QueueReceiver or QueueBrowser); in the publish/subscribe delivery model, the consumer is a subscriber (TopicSubscriber).

data store     A database where information (durable subscriptions, data about destinations, persistent messages, auditing data) needed by the broker is permanently stored.

delivery mode     An indicator of the reliability of messaging: whether messages are guaranteed to be delivered and successfully consumed once and only once (persistent delivery mode) or guaranteed to be delivered at most once (non-persistent delivery mode).

delivery model     The model by which messages are delivered: either point-to-point or publish/subscribe. In JMS there are separate programming domains for each, using specific client runtime objects and specific destination types (queue or topic), as well as a unified programming domain.

delivery policy     A specification of how a queue is to route messages when more than one message consumer is registered. The policies are: single, failover, and round-robin.

destination     The physical destination in an MQ message server to which produced messages are delivered for routing and subsequent delivery to consumers. This physical destination is identified and encapsulated by an administered object that a client uses to specify the destination for which it is producing messages and/or from which it is consuming messages.

domain     A set of objects used by JMS clients to program JMS messaging operations. There are two programming domains: one for the point-to-point delivery model and one for the publish/subscribe delivery model.

MQ client runtime     Software that provides JMS clients with an interface to the MQ message server. The client runtime supports all operations needed for clients to send messages to destinations and to receive messages from such destinations.

MQ message server     Software that provides delivery services for an MQ messaging system, including connections to JMS clients, message routing and delivery, persistence, security, and logging. The message server maintains physical destinations to which JMS clients send messages, and from which the messages are delivered to consuming clients.

JMS (Java Message Service)     A standard set of interfaces and semantics that define how a Java client accesses the facilities of a message service. These interfaces provide a standard way for Java programs to create, send, receive, and read messages.

JMS provider     A product that implements the JMS interfaces for a messaging system and adds the administrative and control functions needed for a complete product.

message selector     A way for a consumer to select messages based on property values (selectors) in JMS message headers. A message service performs message filtering and routing based on criteria placed in message selectors.

message service     See MQ message server.

messages     Asynchronous requests, reports, or events that are consumed by JMS clients. A message has a header (to which additional fields can be added) and a body. The message header specifies standard fields and optional properties. The message body contains the data that is being transmitted.

messaging     A system of asynchronous requests, reports, or events used by enterprise applications that allows loosely coupled applications to transfer information reliably and securely.

point-to-point delivery model     Producers address messages to specific queues; consumers extract messages from queues established to hold their messages. A message is delivered to only one message consumer.

produce     Passing a message to the client runtime for delivery to a destination.

producer     An object (MessageProducer) created by a session that is used for sending messages to a destination. In the point-to-point delivery model, a producer is a sender (QueueSender); in the publish/subscribe delivery model, a producer is a publisher (TopicPublisher).

publish/subscribe delivery model     Publishers and subscribers are generally anonymous and may dynamically publish or subscribe to a topic. The system distributes messages arriving from a topic’s multiple publishers to its multiple subscribers.

queue     An object created by an administrator to implement the point-to-point delivery model. A queue is always available to hold messages even when the client that consumes its messages is inactive. A queue is used as an intermediary holding place between producers and consumers.

session     A single threaded context for sending and receiving messages. This can be a queue session or a topic session.

topic     An object created by an administrator to implement the publish/subscribe delivery model. A topic may be viewed as node in a content hierarchy that is responsible for gathering and distributing messages addressed to it. By using a topic as an intermediary, message publishers are kept separate from message subscribers.

transaction     An atomic unit of work which must either be completed or entirely rolled back.

user group     The group to which the user of a MQ client belongs for purposes of authorizing access to MQ message server resources, such as connections and destinations.

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