The PFNMAP privilege lets a user's process create and map
page frame number (PFN) global sections to specific pages of physical
memory or I/O device registers, no matter who is using the pages
or registers. Such a privileged process can also delete PFN-based
global sections with the system service $DGBLSC.
Exercise caution when granting this privilege. If unqualified
user processes have unrestricted access to physical memory, the
operating system and service to other processes can be easily disrupted.
Such disruptions can include failure of the system, destruction
of all system and user data, and exposure of confidential information.
HP OpenVMS Guide to System Security
Security for the System Administrator
