IBM GC34-5557-00 manual Messages and Queues What is a Queue?, MQSeries Objects

Messages and Queues

What is a Queue?

A queue is a data structure that stores messages. The messages may be put on the queue by applications or by a queue manager as part of its normal operation.

Queues exist independently of the applications that use them. A queue can exist in main storage (if it is temporary), on disk or similar auxiliary storage (if it must be kept in case of recovery), or in both places (if it is currently being used, and must also be kept for recovery). Each queue belongs to a queue manager, which is responsible for maintaining it. The queue manager puts the messages it receives onto the appropriate queue.

Queues can exist either in your local system, in which case they are called local queues, or at another queue manager, in which case they are called remote queues.

Applications use MQI calls to send and receive messages. One application can put a message on a queue and another application can retrieve the message from the same queue.

MQSeries Objects

An MQSeries object is a recoverable resource that is managed by MQSeries. Many of the tasks that are described in this chapter involve manipulating the following types of MQSeries object:

vQueue managers

vQueues

vProcess definitions

vChannels

vNamelists

MQSeries creates default objects for you when you create a queue manager.

Each object has a name associated with it. You can specify that name in MQSeries commands and MQI calls to refer to the object. Names must be unique within each of the object types. For example, you can have a queue and a process with the same name, but you cannot have two queues with the same name.

Chapter 1. About MQSeries 3