WebSphere MQ messaging services

A service represents a destination that applications send messages to or receive messages from.

In WebSphere® MQ a destination is called a message queue. A queue resides in a queue manager. The parameters that describe the messages on a queue are defined in a service by the systems administrator.

Point-to-point application

In a point-to-point application, the sending application knows the destination of the message. Point-to-point applications can be send and forget, or datagrams, in which a reply to the message is not required. Point-to-point applications can be request or response messages, where the message specifies the destination for the response message. For example, the correlation identifier in the Table 3 configuration table, is used for a request/reply type of application in MQ user defined functions

Publish or subscribe application

In a publish/subscribe application, the providers of information (publishers) are separate from the consumers of that information (subscribers).

Publishers supply information about a subject by sending it to a broker. The subject is identified by a topic. A publisher can publish information on more than one topic, and many publishers can publish information on a particular topic.

Subscribers decide what information might be of interest, and subscribes to the relevant topics by sending a message to the broker. When information is published on one or the topics of interest, the broker sends it to the subscriber.

There can be many brokers in a publish or subscribe system. The brokers communicate with each other to exchange subscription requests and publications. A publication is propagated to another broker if a subscription to that topic exists on the other broker.

Types of service

Different types of service are defined to specify the mapping from the messaging interface to resources in the messaging network.
  • Senders and receivers establish one-way communication pipes for sending and receiving messages.
  • A publisher contains a sender that is used to publish messages to a publish or subscribe broker.
  • A subscriber contains a sender, that is used to subscribe to a publish or subscribe broker, and a receiver, that is used to receive publications from the broker.
The messaging interface provides default services that are used unless otherwise specified by the application program. You can also define your own service that is customized and stored in the configuration tables when calling a function. Many of the options used by the services are contained in a policy.