Adding a new, interconnected cluster

Add a new cluster that shares some queue managers with an existing cluster.

Before starting

Note:

For changes to a cluster to be propagated throughout the cluster, at least one full repository must always be available. Ensure that your repositories are available before starting this task.
Before starting this task, check for queue-name clashes and understand the consequences. We might need to rename a queue, or set up queue aliases before we can proceed.

Scenario:

An IBM MQ cluster has been set up as described in Convert an existing network into a cluster.
A new cluster called MAILORDER is to be implemented. This cluster comprises four of the queue managers that are in the CHNSTORE cluster; CHICAGO, CHICAGO2, SEATTLE, and ATLANTA, and two additional queue managers; HARTFORD and OMAHA. The MAILORDER application runs on the system at Omaha, connected to queue manager OMAHA. It is driven by the other queue managers in the cluster putting messages on the MORDERQ queue.
The full repositories for the MAILORDER cluster are maintained on the two queue managers CHICAGO and CHICAGO2.
The network protocol is TCP.

About this task

Follow these steps to add a new, interconnected cluster.

Procedure

Create a namelist of the cluster names. The full repository queue managers at CHICAGO and CHICAGO2 are now going to hold the full repositories for both of the clusters CHNSTORE and MAILORDER. First, create a namelist containing the names of the clusters. Define the namelist on CHICAGO and CHICAGO2, as follows:
```
DEFINE NAMELIST(CHAINMAIL)
DESCR('List of cluster names')
NAMES(CHNSTORE, MAILORDER)
```
Alter the two queue manager definitions. Now alter the two queue manager definitions at CHICAGO and CHICAGO2. Currently these definitions show that the queue managers hold full repositories for the cluster CHNSTORE. Change that definition to show that the queue managers hold full repositories for all clusters listed in the CHAINMAIL namelist. Alter the CHICAGO and CHICAGO2 queue manager definitions:
```
ALTER QMGR REPOS(' ') REPOSNL(CHAINMAIL)
```
Alter the CLUSRCVR channels on CHICAGO and CHICAGO2. The CLUSRCVR channel definitions at CHICAGO and CHICAGO2 show that the channels are available in the cluster CHNSTORE. We need to change the cluster-receiver definition to show that the channels are available to all clusters listed in the CHAINMAIL namelist. Change the cluster-receiver definition at CHICAGO:
```
ALTER CHANNEL(CHNSTORE.CHICAGO) CHLTYPE(CLUSRCVR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
At CHICAGO2, enter the command:
```
ALTER CHANNEL(CHNSTORE.CHICAGO2) CHLTYPE(CLUSRCVR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
Alter the CLUSSDR channels on CHICAGO and CHICAGO2. Change the two CLUSSDR channel definitions to add the namelist. At CHICAGO, enter the command:
```
ALTER CHANNEL(CHNSTORE.CHICAGO2) CHLTYPE(CLUSSDR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
At CHICAGO2, enter the command:
```
ALTER CHANNEL(CHNSTORE.CHICAGO) CHLTYPE(CLUSSDR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
Create a namelist on SEATTLE and ATLANTA. Because SEATTLE and ATLANTA are going to be members of more than one cluster, create a namelist containing the names of the clusters. Define the namelist on SEATTLE and ATLANTA, as follows:
```
DEFINE NAMELIST(CHAINMAIL)
DESCR('List of cluster names')
NAMES(CHNSTORE, MAILORDER)
```
Alter the CLUSRCVR channels on SEATTLE and ATLANTA. The CLUSRCVR channel definitions at SEATTLE and ATLANTA show that the channels are available in the cluster CHNSTORE. Change the cluster-receive channel definitions to show that the channels are available to all clusters listed in the CHAINMAIL namelist. At SEATTLE, enter the command:
```
ALTER CHANNEL(CHNSTORE.SEATTLE) CHLTYPE(CLUSRCVR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
At ATLANTA, enter the command:
```
ALTER CHANNEL(CHNSTORE.ATLANTA) CHLTYPE(CLUSRCVR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
Alter the CLUSSDR channels on SEATTLE and ATLANTA. Change the two CLUSSDR channel definitions to add the namelist. At SEATTLE, enter the command:
```
ALTER CHANNEL(CHNSTORE.CHICAGO) CHLTYPE(CLUSSDR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```
At ATLANTA, enter the command:
```
ALTER CHANNEL(CHNSTORE.CHICAGO2) CHLTYPE(CLUSSDR)
CLUSTER(' ') CLUSNL(CHAINMAIL)
```

Define CLUSRCVR and CLUSSDR channels on HARTFORD and OMAHA. On the two new queue managers HARTFORD and OMAHA, define cluster-receiver and cluster-sender channels. It does not matter in which sequence you make the definitions. At HARTFORD, enter:

DEFINE CHANNEL(MAILORDER.HARTFORD) CHLTYPE(CLUSRCVR) TRPTYPE(TCP)
CONNAME(HARTFORD.CHSTORE.COM) CLUSTER(MAILORDER)
DESCR('Cluster-receiver channel for HARTFORD')

DEFINE CHANNEL(MAILORDER.CHICAGO) CHLTYPE(CLUSSDR) TRPTYPE(TCP)
CONNAME(CHICAGO.CHSTORE.COM) CLUSTER(MAILORDER)
DESCR('Cluster-sender channel from HARTFORD to repository at CHICAGO')

At OMAHA, enter:

DEFINE CHANNEL(MAILORDER.OMAHA) CHLTYPE(CLUSRCVR) TRPTYPE(TCP)
CONNAME(OMAHA.CHSTORE.COM) CLUSTER(MAILORDER)
DESCR('Cluster-receiver channel for OMAHA')

DEFINE CHANNEL(MAILORDER.CHICAGO) CHLTYPE(CLUSSDR) TRPTYPE(TCP)
CONNAME(CHICAGO.CHSTORE.COM) CLUSTER(MAILORDER)
DESCR('Cluster-sender channel from OMAHA to repository at CHICAGO')

Define the MORDERQ queue on OMAHA. The final step to complete this task is to define the queue MORDERQ on the queue manager OMAHA. At OMAHA, enter:
```
DEFINE QLOCAL(MORDERQ) CLUSTER(MAILORDER)
```
Check that the cluster changes have been propagated. Check that the definitions you created with the previous steps have been propagated though the cluster. Issue the following commands on a full repository queue manager:
```
DIS QCLUSTER (MORDERQ)
DIS CLUSQMGR
```

Results

The cluster set up by this task is shown in Figure 1.

Now we have two overlapping clusters. The full repositories for both clusters are held at CHICAGO and CHICAGO2. The mail order application that runs on OMAHA is independent of the inventory application that runs at CHICAGO. However, some of the queue managers that are in the CHNSTORE cluster are also in the MAILORDER cluster, and so they can send messages to either application. Before carrying out this task to overlap two clusters, be aware of the possibility of queue-name clashes.

Suppose that on NEWYORK in cluster CHNSTORE and on OMAHA in cluster MAILORDER, there is a queue called ACCOUNTQ. If you overlap the clusters and then an application on SEATTLE puts a message to the queue ACCOUNTQ, the message can go to either instance of the ACCOUNTQ.

What to do next

Suppose you decide to merge the MAILORDER cluster with the CHNSTORE cluster to form one large cluster called CHNSTORE.

To merge the MAILORDER cluster with the CHNSTORE cluster, such that CHICAGO and CHICAGO2 hold the full repositories:

Alter the queue manager definitions for CHICAGO and CHICAGO2, removing the REPOSNL attribute, which specifies the namelist ( CHAINMAIL), and replacing it with a REPOS attribute specifying the cluster name ( CHNSTORE). For example:
```
ALTER QMGR(CHICAGO) REPOSNL(' ') REPOS(CHNSTORE)
```
On each queue manager in the MAILORDER cluster, alter all the channel definitions and queue definitions to change the value of the CLUSTER attribute from MAILORDER to CHNSTORE. For example, at HARTFORD, enter:
```
ALTER CHANNEL(MAILORDER.HARTFORD) CLUSTER(CHNSTORE)
```
At OMAHA enter:
```
ALTER QLOCAL(MORDERQ) CLUSTER(CHNSTORE)
```
Alter all definitions that specify the cluster namelist CHAINMAIL, that is, the CLUSRCVR and CLUSSDR channel definitions at CHICAGO, CHICAGO2, SEATTLE, and ATLANTA, to specify instead the cluster CHNSTORE.

From this example, we can see the advantage of using namelists. Instead of altering the queue manager definitions for CHICAGO and CHICAGO2 we can alter the value of the namelist CHAINMAIL. Similarly, instead of altering the CLUSRCVR and CLUSSDR channel definitions at CHICAGO, CHICAGO2, SEATTLE, and ATLANTA, we can achieve the required result by altering the namelist.

Parent topic: Convert an existing network into a cluster

Related tasks

Removing a cluster network