https://www.ibm.com/docs/en/ims/15.5.0?topic=set-dfsdscty-member-ims-proclib-data
IMS 15.5 - System definition - DFSDSCTy member of the IMS PROCLIB data set
Use the DFSDSCTy member of the IMS PROCLIB data set to specify override descriptors for the Extended Terminal Option (ETO), including logon descriptors, MFS...