MQI client: Client Channel Definition Table (CCDT)
You can connect an IBM® MQ MQI client application to any level of queue manager. If a 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.
When a client uses a CCDT file that was generated using a newer version of IBM MQ, only channel attributes within the CCDT that were available at the client's IBM MQ version are considered during negotiation with the queue manager. Channel attributes present in the CCDT that were added in newer versions of IBM MQ will be ignored by older clients.
Version of originating queue manager for a CCDT
In earlier releases before IBM MQ 9.0, clients can use a CCDT built by the same or earlier version queue manager, but there was previously a restriction on clients using a CCDT built by a later version queue manager. However, this restriction is removed in IBM MQ 9.0.
From IBM MQ 9.0, if a client uses a CCDT, it can use a CCDT built by a later version queue manager, as well as a CCDT built by the same, or earlier version of queue manager.
The same restriction on the use of CCDTs originating from later version queue managers is also removed in IBM MQ 8.0, 7.5 and 7.1 by APARs IT10863 and IT11547. for more information, see the technote MQ 7.x, 8.0 and 9.0 compatibility with previous versions - including usage of CCDT files, JMS .bindings, SSL/TLS.
Common migration scenarios
If, for example, you upgrade a queue manager from an earlier release to a later release, and you do not create new CCDTs for its clients, the clients connect to the later release queue manager without any changes being required. Client behavior might change as a result of changes to the queue manager.
Another common migration scenario is to update some queue managers and some clients to a later release, leaving other queue managers and clients at the earlier release. In this scenario, you want to update the CCDT for the IBM MQ MQI clients that are connected to the later release queue managers to that later release so that those clients can fully use the function in the later release. The new clients can also connect to the earlier release queue managers. Existing clients connect to queue managers in both releases. In order that the clients in the later release can use the new function in that release, you must deploy a CCDT that has been generated by a queue manager in that new release. Clients in the earlier release can continue to use the CCDT for that earlier release. Both sets of clients can connect to both sets of queue managers, regardless of the CCDT they are using.