Issue:
Periodic "RMOCPP05 WAITING FOR CHECKPOINT" messages are issued, and the system hangs.
Resolution:
In this instance, the client was using Workload Manager (WLM), and Deliver (RMO) was a victim of WLM.
WLM was limiting the service class that RMO runs in.
There were many people using the CICS integrated test environment, and WLM was giving that activity all of the cycles.