The definitions of the IBM MQ terms coexistence, compatibility, and interoperability.
Coexistence
Is being able to install and run two or more versions of the same program on the same server. For IBM MQ, it normally means installing and running multiple versions of IBM MQ on a server.
Compatibility
Is the ability to run applications from one level of queue manager with an earlier, or previous level, of the queue manager.
If you are using a message channel agent (MCA) channel, any version and release of an IBM MQ queue manager can connect, using an MCA channel, to any version and release of another IBM MQ queue manager.
The MCA channel is automatically configured to the latest version of protocol that is supported by both ends of the channel.
Compatibility is also the ability to run client applications with different versions of the IBM MQ MQI client, and different levels of the queue manager.
Interoperability
Is mainly the ability to exchange messages between different versions of IBM MQ. It can also mean the interoperability between others things, such as publish/subscribe brokers, or between components such as the IBM MQ classes for JMS and WebSphere Application Server.
Maintaining the compatibility, coexistence, and interoperability of IBM MQ is important in order to preserve the investment you make in applications and administrative procedures.
Three areas to which this objective does not apply to as rigidly, are:
GUI interfaces, such as IBM MQ Explorer.
Information for service, such as FFST files and traces.
Error messages. The text in an error message might change, to make the wording clearer or more accurate.