Compatibility between different versions of an IBM MQ client and a queue manager

Any supported version and release of an IBM® MQ client can connect to any supported version and release of an IBM MQ queue manager. Supported IBM MQ clients are all clients included with the main MQ product. This includes IBM MQ Internet Pass-Thru (MQIPT). The MQI channel is automatically configured to the latest version that both the client and server support. If the client and server are different versions, the client application must use only the functions in the earlier version.

The compatibility between clients and queue managers applies only to the version and release (V.R) of the product. The statement of compatibility does not necessarily apply to the modification and fix pack level (M.F) of the product.

If there are known problems at a specific V.R.M.F of the product, upgrade to a more recent fix pack for the same Version.Release.

When you upgrade a queue manager to a different version, you automatically upgrade IBM MQ libraries. The libraries are used by IBM MQ client and server applications running on the same server as the queue manager. To access new functions from remote clients, you must also upgrade the IBM MQ client installation on remote workstations. The IBM MQ client includes the IBM MQ client libraries.

Remote clients that have not been upgraded continue to work with an upgraded queue manager. In rare cases, the behavior of the client application might change. See Changes that affect migration.

Remote clients that are connected to upgraded queue managers can use the new functions in the release. If an upgraded remote client is connected to a queue manager that has not been upgraded, it must not use new functions. In rare cases, the behavior of the client might change. See Changes that affect migration.

You can generally assume that upgrading the IBM MQ client does not require you to recompile or relink the client application. You can also continue to use the same connection to the queue manager. If changes are required, they are identified in Migrating a queue manager on Windows, for the particular migration path and platform you are concerned with.

The Client Channel Definition Table (CCDT) is an interface to customize the connection between an IBM MQ client and a queue manager. Entries in the tables are client connections, which are defined using a queue manager. The version of a CCDT is the version of the queue manager used to define the client connections. If an IBM MQ client uses CCDT to connect to a queue manager, the CCDT can be at a version greater than, less than, or equal to that of the client.

You can connect to a queue manager with an earlier IBM MQ client or an earlier CCDT. If you are using a CCDT, and you plan to use new client channel configuration options, such as shared conversations, you must upgrade the CCDT, and therefore the IBM MQ client installation, to the new version.