In February, we came across an unmapped problem in our environment. In short, our experts identified that the problem occurred because there was a specific CICS transaction, which was started in duplicate. And our environment did not warn that in any of the tools because it was not mapped.
There is a monitoring to identify a drop in this transaction, but we had not anticipated this, because the partner did not inform us that this was a problem for the operation of the service.
This transaction x must be active for the service to work.
You could put CTR2 into a TRANCLASS with a MAXACTIVE of 1. If you did this, CICS would prevent more than one CTR2 transaction from being active.
Also, if you have SYSVIEW, there is a TCLSACT CTHRESH definition you could create to monitor this. Again, you would need to place CTR2 into its own TRANCLASS, then set a CTHRESH definition for that TRANCLASS name to be in problem status if it goes above 1 for the TCLSACT metric.
(This same post also appears in the Netmaster communities.)