IMS cannot connect to WebSphere MQ

Problem
The IMS(TM) adapter cannot connect to WebSphere MQ.
Symptoms
IMS remains operative. The IMS adapter issues these messages for control region connect: For details, see the WebSphere MQ for z/OS Messages and Codes manual.

If an IMS application program tries to access WebSphere MQ while the IMS adapter cannot connect, it can either receive a completion code and reason code, or terminate abnormally. This depends on the value of the REO option in the SSM member of IMS PROCLIB.

System action
All connection errors are also reported in the IMS message DFS3611.
System programmer action
None.
Operator action

Analyze and correct the problem, then restart the connection with the IMS command:

/START SUBSYS subsysname

IMS requests the adapter to resolve in-doubt units of recovery.