2.17 I'm looking for a method to turn on/off the ability for users to use CTRL-BREAK to interrupt a process. Obviously this can be done at the LOGON UDC level, but I want to be able to do this within a command file.

You can disable the CTRL-BREAK by putting OPTION NOBREAK in the first line of your command file. There is a catch though -- don't use it on a REMOTE command file. Be aware that if you press CTRL-BREAK on a remote command file that has OPTION NOBREAK, your VT session will hang. The CI will be stuck in a perpetual "Terminal Read Wait" until someone does an :ABORTIO on the virtual LDEV.