Connecting applications in a multiple installation environment

On AIX®, Linux®, and Windows systems, if IBM® MQ libraries are loaded, IBM MQ automatically uses the appropriate libraries without you needing to take any further action. IBM MQ uses libraries from the installation associated with the queue manager that the application connects to.

The following concepts are used to explain the way applications connect to IBM MQ:

Linking: When the application is compiled, the application is linked to the IBM MQ libraries to get the function exports that are then loaded when the application runs.
Loading: When the application is run, the IBM MQ libraries are located and loaded. The specific mechanism used to locate the libraries varies by operating system, and by how the application is built. For more information about how to locate and load libraries in a multiple installation environment, see Loading IBM MQ libraries.
Connecting: When the application connects to a running queue manager, for example, using a MQCONN or MQCONNX call, it connects using the loaded IBM MQ libraries.

When a server application connects to a queue manager, the loaded libraries must come from the installation associated with the queue manager. With multiple installations on a system, this restriction introduces new challenges when choosing the mechanism that the operating system uses to locate the IBM MQ libraries to load:

When the setmqm command is used to change the installation associated with a queue manager, the libraries that need to be loaded change.
When an application connects to multiple queue managers that are owned by different installations, multiple sets of libraries need to be loaded.

However, if IBM MQ, libraries, are located and loaded, IBM MQ then loads and uses the appropriate libraries without you needing to take any further action. When the application connects to a queue manager, IBM MQ loads libraries from the installation that the queue manager is associated with.

Migration scenarios and connecting applications with multiple installations is considered in more detail in Multi-installation queue manager coexistence on AIX, Linux, and Windows.

For more information about how to load IBM MQ libraries, see Loading IBM MQ libraries.

Support and restrictions

If any of the following IBM MQ libraries, are located and loaded, the product can automatically load and use the appropriate libraries:

The C server libraries
The C++ server libraries
The XA server libraries
The COBOL server libraries
The COM+ server libraries
.NET in unmanaged mode

IBM MQ also automatically loads and uses the appropriate libraries for Java and JMS applications in bindings mode.

There are a number of restrictions for applications using multiple installations. For more information, see Restrictions for applications using multiple installations.