Migrating from a single instance to a multi-instance queue manager on UNIX and Linux

To migrate a single instance queue manager, to a multi-instance queue manager, on UNIX and Linux®, 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.For a list of tested environments, see Testing statement for IBM® MQ multi-instance queue manager file systems. Other environments might work; a test tool is provided with IBM 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 statement for IBM MQ multi-instance queue manager file systems. 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 IBM 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 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 in Example directory configurations on UNIX.

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 on the shared drive. /MQHA is owned by the user and group mqm and has the access permissions rwx.
Copy the queue manager data and the logs to the share.
Follow the procedure to back up the queue manager described in Backing up queue manager data.
Note: Unlike on Windows, the hamvmqm utility cannot be used on UNIX.
Update the queue manager configuration information stored on the current queue manager server by completing the following steps:
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 IBM MQ mqs.ini file, which is typically in the /var/mqm directory on UNIX and Linux:
```
DataPath= share/data/QMgrName
```
  where QMgrName is the Directory name in the QueueManager: stanza in the mqs.ini file and 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.
```
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 the following connection name:
```
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 IBM 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.