Migrating from a single instance to a multi-instance queue manager

To migrate a single instance queue manager to a multi-instance queue manager, you must move the queue manager data to a shared directory, and reconfigure the queue manager on two other servers.

Before you begin

You must check the prerequisites for running a multi-instance queue manager as part of this task. Some environments have been tested with multi-instance queue managers, and are known to work. They are AIX®, Red Hat Linux®, SUSE Linux Enterprise Server, HP-UX with the file system on Linux Red Hat, IBM® i, and Windows Server. See Testing and support statement for WebSphere® MQ multi-instance queue managers for the latest list of tested environments. The support statement has detailed version and prerequisite information for each environment it lists. Other environments might work; a test tool is provided with WebSphere MQ to assist you in qualifying other environments.

You must have three servers to run a multi-instance queue manager. One server has a shared file system to store the queue manager data and logs. The other servers run the active and standby instances of the queue manager.

About this task

You have a single-instance queue manager that you want to convert to a multi-instance queue manager. The queue manager conversion itself is straightforward, but you must do other tasks to create a fully automated production environment.

You must check the prerequisites for a multi-instance queue manager, set up the environment and check it. You must set up a monitoring and management system to detect if the multi-instance queue manager has failed and been automatically restarted. You can then find out what caused the restart, remedy it, and restart the standby. You must also modify applications, or the way applications are connected to the queue manager, so that they can resume processing after a queue manager restart.

Procedure

Check the operating system that you are going to run the queue manager on, and the file system on which the queue manager data and logs are stored on. Check that they can run a multi-instance queue manager.
1. Consult Testing and support statement for WebSphere MQ multi-instance queue managers. See whether the combination of operating system and file system is tested and capable of running a multi-instance queue manager.
  - A shared file system must provide lease-based locking to be adequate to run multi-instance queue managers. Lease-based locking is a recent feature of some shared file systems, and in some case fixes are required. The support statement provides you with the essential information.
2. Run amqmfsck to verify that the file system is configured correctly.
  - File systems are sometimes configured with performance at a premium over data integrity. It is important to check the file system configuration. A negative report from the amqmfsck tool tells you the settings are not adequate. A positive result is an indication that the file system is adequate, but the result is not a definitive statement that the file system is adequate. It is a good indication.
3. Run the integrity checking application provided in the technote, Testing a shared file system for compatibility with WebSphere MQ Multi-instance Queue Managers.
  - The checking application tests that the queue manager is restarting correctly.
Configure a user and group to be able to access a share on the networked file system from each server that is running a queue manager instance.
- On Windows, the security IDs (SIDs) of the mqm group can be different; see Windows domains and multi-instance queue managers .
- On UNIX and Linux, the uid and gid for mqm in /etc/password must be the same on each system; see Create a multi-instance queue manager on Linux.
Set up a directory for the share on the networked file system with the correct access permissions.
- A typical configuration is to set up a single shared directory that contains all data and log directories for all queue managers that use the shared disk; see Share named qmgrs and log directories (version 7.0.1 onwards) in Example directory configurations on UNIX systems.
- For example, create a root directory on the share called MQHA that has subdirectories data and logs. Each queue manager creates its own data and log directories under data and logs. Create MQHA with the following properties:
- On Windows, create drive\MQHA on the shared drive. The owner is a member of mqm. mqm must have full-control authority. Create a share for drive\MQHA.
- On UNIX, create /MQHA on the shared drive. /MQHA is owned by the user and group mqm and has the access permissions rwx.
- If you are using an NFS v4 file server, add the line /MQHA * rw,sync,no_wdelay,fsid=0) to etc/exports, and then start the NFS daemon: /etc/init.d/nfs start.
Copy the queue manager data and the logs to the share.
- You can choose to copy files manually, by following the procedure to back up the queue manager. On Windows, you can run the hamvmqm command to move the queue manager data to the share. The hamvmqm command works for queue managers created before version 7.0.1, and not reconfigured with a datapath, or for queue managers that do not have a DataPath configuration attribute. Choose one of these methods:
- Follow the instructions in Backing up queue manager data, copying the queue manager data to the share. You must use this method if the DataPath configuration attribute is specified for this queue manager.
- Stop the queue manager, and then type the command,
```
hamvmqm /m /dd share\data /dd share\logs
```
  Where share is to be the location of the data and logs that you created in step 3.
Update the queue manager configuration information stored on the current queue manager server.
- If you moved the queue manager data and logs by running the hamvmqm command, the command has already modified the configuration information correctly for you.
- If you moved the queue manager data and logs manually, you must complete the following steps.
- On Windows:
  1. Modify the log registry key:
```
HKEY_LOCAL_MACHINE\SOFTWARE\IBM\MQSeries\CurrentVersion\Configuration\QueueManager\QMgrName\Log
"LogPath"="share\\logs\\QMgrName\\"
```
  2. Modify the Prefix registry key:
```
HKEY_LOCAL_MACHINE\SOFTWARE\IBM\MQSeries\CurrentVersion\Configuration\QueueManager\QMgrName
"Prefix"="share\\data"
```
- On UNIX, and Linux,
  1. Modify the Log: stanza in the queue manager qm.ini file, which is on the share:
```
LogPath=share/logs/QMgrName
```
  2. Modify the QueueManager: stanza in the WebSphere MQ mqs.ini file, which is typically in the /var/mqm directory on UNIX and Linux:
```
DataPath=share/data/QMgrName
```
- Where, QMgrName is the representation of the queue manager name in the existing registry key on Windows. QMgrName is the Directory name in the QueueManager: stanza in the mqs.ini file on UNIX, and Linux. share is share where the data and logs are moved to.
Add the queue manager configuration information to the new queue manager server.
1. Run the dspmqinf command to display the queue manager information
  - Run the command on the server that ran the queue manager in version 6.0.
```
dspmqinf -o command QMgrName
```
  The command output is formatted ready to create a queue manager configuration.
  addmqinf -s QueueManager -v Name=QMgrName -v Directory=QMgrName -v Prefix=d:\var\mqm Datapath=\share\data\QMgrName
2. Create a queue manager configuration on the other server.
  - Run the addmqinf command copied from the previous output
Add the network address of the new server to the connection name in client and channel definitions.
1. Find all the client, sender, and requester TCPIP settings that refer to the server.
  - Client settings might be in Client Definition Tables (CCDT), in environment variables, in Java properties files, or in client code.
  - Cluster channels automatically discover the connection name of a queue manager from its cluster receiver channel. As long as the cluster receiver channel name is blank or omitted, TCPIP discovers the IP address of the server hosting the queue manager.
2. Modify the connection name for each of these connections to include the TCPIP addresses of both servers that are hosting the multi-instance queue manager.
  - For example, change:
```
echo DISPLAY CHANNEL(ENGLAND) CONNAME | runmqsc QM1
```
```
5724-H72 (C) Copyright IBM Corp. 1994, 2024. ALL RIGHTS RESERVED.
Starting MQSC for queue manager QM1.
1: DISPLAY CHANNEL(ENGLAND) CONNAME
AMQ8414: Display Channel details.
CHANNEL(ENGLAND) CHLTYPE(SDR)
CONNAME(LONDON)
```
  - Into:
```
echo ALTER CHANNEL(ENGLAND) CHLTYPE(SDR) CONNAME('LONDON, BRISTOL') | runmqsc QM1
```
Update your monitoring and management procedures to detect the queue manager restarting.
Update client applications to be automatically reconnectable, if appropriate.
Update the start procedure for your WebSphere MQ applications to be started as queue manager services.
Start each instance of the queue manager, permitting them to be highly available.
- The first instance of the queue manager that is started becomes the active instance.
- Issue the command twice, once on each server.
```
strmqm -x QMgrName
```

What to do next

To get the highest availability out of multi-instance queue managers, you must design client applications to be reconnectable and server applications to be restartable; see Application recovery.