If you have a user task that is waiting for resource type ALLOCATE, it has attempted to get a session with another CICS® region, but all the sessions are in use. Consider defining a greater number of sessions, which should solve the problem. For guidance about this, see the CICS Resource Definition Guide and the CICS Intercommunication Guide.
If you otherwise have a problem that you have identified as an interregion or an intersystem communication wait, investigate it as for terminal waits. This is dealt with in Investigating terminal waits.
The method of debugging is the same in each case. You need to consider the access method, terminal control, and the "terminal" itself.
For interregion and intersystem communication, the remote region or system is the terminal. Its status can be found using the same online or offline techniques that you would use to find the status of a physical terminal. The status may lead you to suspect that the task running in the remote region is the cause of the problem, and you then need to investigate why that task is waiting. So you could find that what started as a terminal wait might, after all, be a wait on some other type of resource.