What Is Cluster

Cluster:
"A cluster is a network of Queue Managers that are logically connected each other. Each cluster must have a unique name."

If you don't use clusters, your Queue Managers are independent and communicating using DQM (Distributed Queue Management).if one Queue Manager needs to send and receive messages from multiple Queue Managers  it must have defined 

1. Remote Queues
2. Transmission Queues
3. Many sender definitions 

If you group Queue Managers in a cluster, the Queue Manager can make the queues that they host available to every other Queue Manager in the cluster.

Any Queue Manager can send and receive messages to and from other Queue Managers in the same cluster without defining remote queues,transmission queues and to many channels.

In every cluster one full repository is must. Two full repositories are strongly recommended by IBM.

Repository

A repository is a collection of information about the Queue Managers that are members of a cluster. Cluster has two types of repositories 

1. Full Repository
2. Partial Repository

Full Repository

A repository Queue Manager hosts a complete set of info about every Queue Manager in the cluster. This set of information is called the repository or some times called as full repository.

Partial Repository

The other queue managers each hold a partial repository, containing information about the subset of queues and queue managers with which they need to communicate. The queue managers build up their partial repositories by making inquiries when they first need to access another queue or queue manager, and by requesting that thereafter they be notified of any new information concerning that queue or queue manager.

Each queue manager stores its repository information in messages on a queue called SYSTEM.CLUSTER.REPOSITORY.QUEUE. The queue managers exchangerepository information in messages on a queue called SYSTEM.CLUSTER.COMMAND.QUEUE.

Default Cluster Queues

SYSTEM.CLUSTER.REPOSITORY.QUEUE

Each queue manager in a cluster has a local queue called SYSTEM.CLUSTER.REPOSITORY.QUEUE. This queue is used to store all the full repository information. This queue is not normally empty.

SYSTEM.CLUSTER.COMMAND.QUEUE

Each queue manager in a cluster has a local queue called SYSTEM.CLUSTER.COMMAND.QUEUE. This queue is used to carry messages to the full repository. The queue manager uses this queue to send any new or changed information about itself to the full repository queue manager and to send any requests for information about other queue managers. This queue is normally empty.

SYSTEM.CLUSTER.TRANSMIT.QUEUE

Each queue manager has a definition for a local queue called SYSTEM.CLUSTER.TRANSMIT.QUEUE. This is the transmission queue for all messages to all queues and queue managers that are within clusters.

SYSTEM.DEF.CLUSSDR

Each cluster has a default CLUSSDR channel definition called SYSTEM.DEF.CLUSSDR. This is used to supply default values for any attributes that you do not specify when you create a cluster-sender channel on a queue manager in the cluster.

SYSTEM.DEF.CLUSRCVR

Each cluster has a default CLUSRCVR channel definition called SYSTEM.DEF.CLUSRCVR. This is used to supply default values for any attributes that you do not specify when you create a cluster-receiver channel on a queue manager in the cluster.