Types Of Queues

What is a queue?

A queue is a data structure used to store messages, Each queue is owned by a queue manager.

Queues can be characterized by the way they are created:

1) Predefined queues are created by an administrator using the appropriate MQSC or PCF commands. Predefined queues are permanent; they exist independently of the applications that use them and survive WebSphere MQ restarts.

2) Dynamic queues are created when an application issues an MQOPEN request specifying the name of a model queue. The queue created is based on a template queue definition, which is called a model queue. You can create a model queue using the MQSC command DEFINE QMODEL

WebSphere MQ queues:

There are four types of queue object available in WebSphere MQ;

1. Local Queue:

A queue that belongs to the local queue manager. A local queue can contain a list of messages waiting to be processed. A safe place to store messages for Prior-To-Delivery, it belongs to the Qmgr to which the application is connected.

SYNTAX:

DEFINE QL(QUEUENAME)

Or define queuelocal(queuename)

The limitations for WebSphere MQ names are:

1. Only the following characters are allowed: A-Z, a-z, 0-9,. (Period), /, _ (Underscore), %

2. A maximum of 48 characters are allowed for the names of:

• Queue managers,
• Queues,
• Processes,
• A maximum of 20 characters are allowed for the names of channels.

The names of WebSphere MQ objects do not imply any structure to the object. All names in WebSphere MQ are case-sensitive

To display queuelocal attributes

SYNTAX:

Display  queuelocal(queuename)

Or dis ql(queuename)

2. Alias Queue Object:

An alias queue allows applications to access a queue by referring to it indirectly in MQI calls. When an alias queue name is used in an MQI call, the name is resolved to the name of either a local or a remote queue at run time. This allows you to change the queues that applications use without changing the application in any way; you merely change the alias queue definition to reflect the name of the new queue to which the alias resolves.

An alias queue is not a queue, but an object that you can use to access another queue.

SYNTAX:

DEINFE QUEUEALIAS(ALIASQUEUENAME) TARGET(TARGETQUEUENAME)

OR

DEFIEN QA(ANYNAME) TARGET(TARGETLOCALQUEUE NAME OR REMOTE QUEUENAME)

Alias target can be local queue or remote queue you can give as per the requirment.

3. Model Queue Object:

A model queue defines a set of queue attributes that are used as a template for creating a dynamic queue. Dynamic queues are created by the queue manager when an application issues an MQOPEN request specifying aqueue name that is the name of a model queue. The dynamic queue that is created in this way is a local queue whose attributes are taken from the model queue definition. The dynamic queue name can be specified by the application, or the queue manager can generate the name and return it to the application.

4. Remote Queue:

A WebSphere MQ object belonging to a local queue manager that defines the attributes of a queue that is owned by another queue manager. The information you specify when you define a remote queue object allows the local queue manager to find the remote queue manager, so that any messages destined for the remote queue go to the correct queue manager.

This is used to provide remote queuename and remote queuemanger name i.e, target queuename and target qmgr name or destination queue name and destination  qmgrname .

SYNTAX :

DEFINE QR(NAMEOFREMOTEQUEUE) RNQME(DESTINANTION QUEUE NAME) RQMNAME(DESTINANTION QMGR NAME) XMITQ(XMITQ NAME)

WebSphere MQ uses some local queues for specific purposes related to its operation:

• Initiation queues,
• Transmission queues,
• Cluster transmission queues,
• Dead-letter queues,
• Command queues,
• Reply-to queues,
• Event queues.