Processing affinities in an IMSplex
If a message must process on a specific IMS system in the IMSplex, IMS assigns the message affinity to that IMS system by appending the IMSID of the IMS system to the destination name. Then, only that IMS can process it.
You can also use the TM and MSC Message Routing and Control user exit routine (DFSMSCE0) to establish affinities between transaction instances and IMS systems in an IMSplex.
Processing affinities in an IMSplex-MSC coexistent configuration
In an MSC network, remote transactions bypass any local affinity the transactions might have to the IMS system that receives them as input. In an IMSplex, remote transactions also cause local affinity to be bypassed. Otherwise, the rules that govern processing affinities in an IMSplex remain unchanged.