WebSphere MQ clustering Questions & Answers.

Qns:What is Cluster?

Ans: A cluster is a group of queue managers set up in such a way that the queue managers can communicate directly with one another over a single network, without the need for transmission queue, channel, and remote queue definitions.

Qns:What are the Advantages of clustering?

Reduced system administration Increased high availability Improved resource utilizationWorkload sharing

Qns:What is the algorithm that is followed by MQ in clustering?

Ans: WebSphere MQ uses a workload management algorithm that uses a round-robin routine to select an available queue manager to route a message to.

Qns: What is Cluster queue manager? A cluster Queue manager is a queue manager that is a member of a cluster. A queue manager can be a member of more than one cluster What happens when we give a Refresh Cluster mqsc command?

Ans: This command issued on a queue manager, the queue manager discard all locally held information about a cluster except the FULL repository information. This enables you to perform a “cold-start” on the cluster.

Qns:How to remove a Qmgr from Cluster?

Ø  Suspend queue manager

Ø  Remove the CLUSRCVR channel definition from the cluster by setting the CLUSTER attribute

Ø  to empty

Ø  Stop the CLUSRCVR channel

Ø  Delete the CLUSSDR channel definition

Qns:What is the use of clustering?

Ans. Due to the use of clustering

1.      The Administrator tasks can be reduced.

2.      We can achieve the Workload balance.

Qns:How many no Full Repository Queue Managers are required for creating a cluster. What is the difference between full and partial repositories?

Ans: In each cluster you must select at least one, preferably two, or possibly more of the queue managers to hold full repositories. A cluster can work quite adequately with only one full repository but using two improves availability. Every cluster has at least one (preferably two) queue managers holding full repositories of information about the queue managers, queues, and channels in a cluster. These repositories also contain requests from the other queue managers in the cluster for updates to the information. 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.

Qns:Where does the information about the messages of a QueueManager are stored when they are in cluster?

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

Qns:What happens when full cluster repository Qmgr goes down?

Ans: If your queue manager is a full repository queue manager, alter the queue manager definition to set the REPOS and REPOSNL attributes to blank. This sends a notification to other queue managers advising them that they must stop sending cluster information to this queue manager.

Qns:When will we use RESET CLUSTER command?

Ans: To forcibly remove a queue manager from the cluster and resets the cluster

Qns:How does a partial repository QM share information with other clusters when the full repos QM is down?
Ans: The cluster continues to work with information from the other full repository. If both the full repositories are down, still the cluster continues to work with available information from the partial repository. A repository handles the request whenever possible but if the chosen repository is not available another repos used. When the first repository becomes available again, it collects the latest new and changed information from the others so that the queue managers are kept in synch. The repository queue manager send messages to each other to be sure that they are both kept up to date with new information about the cluster

Qns: Algorithm for workload balancing?

Ans: Round Robin

Qns: How do I set up a cluster and add a new QM to a cluster?

Determine to which full repository the qmgr has to point to get cluster information, Define the CLUSRCVR channel, Define a CLUSSDR channel on queue manager.

Qns: Components of a cluster?

Ans: The components of a cluster are a group of queue managers.(more than one) Cluster receiver channel- to communicate with any cluster queue manager Cluster sender channel- to communicate with any cluster queue manager The cluster sender channel points to a full repository queue manager Cluster transmission queue One transmission queue to transmit message to any cluster queue
Cluster queue A queue that is available to all cluster queue managers.

Qns: How many Transmission Queues are present in a Queue manager present in a Cluster?

Ans: ONE.

Qns: When defining a Cluster sender channel, for example if there is more than one instance in the cluster what will happen?

Qns:How many cluster channel definitions are required for a QM in a cluster?

Ans: TWO cluster channel definitions are required: Cluster Sender channel and Cluster Receiver channel.

Qns: What is Cluster queue how is it defined?

Ans: A cluster queue is a queue that is hosted by a cluster queue manager and made available to other queue managers in the cluster. The cluster queue manager makes a local queue definition for the queue, specifying the name of the cluster where the queue is to be found. This definition has the effect of showing the other queue managers in the cluster that the queue is there. The other queue managers in the cluster can put messages to a cluster queue without needing a corresponding remote-queue definition.

Qns: What makes clustering work?

Ans: Defining a cluster-receiver channel has the effect of introducing a queue manager to one of the full repository queue managers. The full repository queue manager updates the information in its full repository accordingly. Then it automatically creates a cluster-sender channel back to the queue manager, and sends the queue manager information about the cluster. Thus a queue manager learns about a cluster and a cluster learns about a queue manager.

Qns: Types of aliases and remote-queue definitions with clusters?

Ans: Queue-manager aliases, reply-to queue aliases, and queue aliases.

Qns:What is a gateway queue manager and advantages of using in a cluster?

Ans: This enables workload balancing for messages coming from outside the cluster.

Qns:How will you keep a cluster secure?

Ø  Stopping the unauthorized Queue manager sending message to your Queue manager.

Ø  Stopping unauthorized Queue manager putting messages on your Queues.

Ø  Stopping Your Queue manager putting messages to remote Queues Preventing Queue manager from joining a cluster: Define a channel security exit program Forcing unwanted queue manager to leave a cluster.

Qns:What is Repository queue manager? What are Full and partial repository?

Ans: A repository queue manager is a cluster queue manager that holds a full repository
A queue manager that hosts a complete set of information about every queue manager in the cluster is referred to as having a full repository for the cluster. The other queue managers in the cluster inquire about the information in the full repositories and build up their own subsets of this information in partial repositories. A partial repository contains information about only those queue managers with which the queue manager needs to exchange messages. The queue managers request updates to the information they need, so that if it changes, the full repository queue manager will send them the new information.

Qns:Where does each queue manager store its repository information?

Ans: SYSTEM.CLUSTER.REPOSITORY.QUEUE.

Qns:Where do the queue managers exchange repository information?

Ans: SYSTEM.CLUSTER.COMMAND.QUEUE.

Qns:What happens when a queue manager fails? What happens if I put-disable a cluster queue? How long do the queue manager repositories retain information?

Ans: It must be 90 days but the Qm sends information to all the QM’s in the cluster to update its information around 30 days.

Qns:Adding a new Queue manager to a cluster?

Ans: Determine the Full repository to which the QM should refer

Define the CLUSRCVR channel.

Define the CLUSSDR channel on the QM.

Review the application for message affinities.

Qns:Removing a cluster queue from a Queue manager?

Ans: Indicate the Queue is no longer available – remove the CLUSTER name from the local queue definition (ALTER QLOCAL(localqueue) CLUSTER(‘’)).

 Disable the Queue – ALTER QLOCAL(localqueue) PUT(DISABLE).

Monitor the Queue until it is EMPTY.

Monitor the channel to ensure that there is no in-doubt messages.

Delete the Queue.

Qns:Removing a Queue Manager form a Cluster?

Ans:

Suspend the QM (SUSPEND QMGR CLUSTER(clusname))

Remove the CLUSRCVR channel definition.

Stop the CLUSRCVR channel.

Delete the CLUSSDR channel definition.

Qns:Converting an existing network to cluster?

Ans:
Alter two QM to make it a FULL repository MQ.

Define CLUSRCVR channel on each Queue manager.

Define CLUSSDR channel on each Queue Manager.

Delete all remote Queue definitions for the existing network.

Qns:What is Workload balancing?

Ans: When a cluster contains more than one instance of the same queue, WebSphere MQ uses a workload management algorithm to determine the best queue manager to route a message . The algorithm uses a round-robin approach to finalize its choice between the suitable queue managers.

Qns: Removing a Cluster network?

Ans:

Remove the cluster queues from the cluster.

Stop all applications that have access to cluster Queue.

Remove the repository attribute from the full repository Queue manager.

Remove Cluster channels on each Queue manager.

Issue REFRESH cluster command on each Queue manager.

Qns:What is key repository?

Ans: IS used to describe the store for digital certificates and their associated private keys.

Qns:What’s the queue where the full and partial repository is stored?

Ans: SYSTEM.CLUSTER.REPOSITORY.QUEUE

Qns: What are the some important MQSC commands that work with cluster?

Ans:
DISPLAY CLUSQMGR SUSPEND CLUSQMGR
RESUME CLUSQMGR REFRESH CLUSTER
RESET CLUSTER