Joined: 06 Jun 2008 Posts: 8154 Location: East Dubuque, Illinois, USA
The only way to know for sure is to look at a CICS start up to find out which lists are being invoked. Those lists will have a set of groups associated with them. IIRC, the first group that contains the file will install that definition.
To delete the files from the region, close and disable the files, delete the active definition from the CDS using CEDA, and install that group.
You should install the new file definition in a group that is invoked during the CICS start processing of the list -- preferably the group that already contains the file definition.