How does the ACF2/IMS interface secure the IMS TRN, and SGN parms in the DFSPBxx members?
ACF2/IMS Interface first verifies if RCF=Y is set to involve ACF2/IMS interface. The RCF=Y parameter is set in the DFSPBIMS member.
After that, since ACF2 protects everything by default, ACF2 forces the security flag to be turned on for SGN and TRN parameters overriding the DFSPBxx members.
Similarly, for the ISIS= parm, if the RASE exit is specified, ACF2 interface will change it to option C.