Multiple installations and application programs

When a local application connects to a queue manager, the application needs to load the libraries from the installation associated with the queue manager. Multiple installations introduce some complexity.

Using the setmqm command

When you use setmqm 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 owned by different installations, multiple sets of libraries need to be loaded.

Note: If you link your applications to IBM® MQ libraries, the applications automatically load the appropriate libraries when the application connects to a queue manager.

Loading IBM MQ libraries in a multi-version environment

How libraries are located depends upon your environment.

If IBM MQ is installed in the default location, existing applications continue to work as before. Otherwise, you might need to rebuild the application or change your configuration.

The order in which libraries are searched, depends upon the platform you are using:

Windows
- The application's directory
- The current directory
- The global and your PATH variables
Other platforms
- LD_LIBRARY_PATH (or LIBPATH/SHLIB_PATH)
- An embedded search path (RPath)
- The default library path

Table 1. Options for loading libraries
Platform	Option	Benefits	Drawbacks
UNIX	Set/change the embedded runtime search path (RPath)	The path is explicit in the way the application is built	You need to recompile and link If you move IBM MQ, you must change RPath
UNIX	Set LD_LIBRARY_PATH or equivalent using setmqenv	Overrides RPath No changes to existing applications Easy to change if you move IBM MQ	Depends on environment variables Possible impacts on other applications
Windows	Set PATH using setmqenv	No changes to existing applications Easy to change if you move IBM MQ	Depends on environment variables Possible impacts on other applications
All	Set the primary installation to IBM WebSphere® MQ 7.1 or later	No changes to existing applications Easy to change the primary installation Similar behavior to previous versions of IBM MQ	UNIX: Relies on /usr/lib in the default search path