RES provides for the interpretation and recognition of maskable resources within the facility. Some examples of maskable resource classes are: DATASET, JESSPOOL, DB2DBASE and DB2COLL. Without RES on the facility, security checks against these resource classes will fail. To see if a resource is maskable or not, issue:
TSS LIST(RDT) RESCLASS(class)
where 'class' is the resource class (ie DATASET).
NORES on a FACILITY means permits for maskable resources will not be loaded into the user's security record when the user signs on. This means that the user is not authorized even though the user has a PERMIT for the maskable resource because the permission was never loaded in storage.
NORES was used to conserve storage in the olden days. RES means that all permissions are loaded into storage. Since the user record is now loaded in 31 bit high private, there are no longer storage concerns when specifying RES on a facility.
TSSSIM finds the correct permit because it is not actually logging into the facility and creating a security record as defined by the facililty RES/NORES Control Option.
Information on the Facility Control Options can be found at the following link: