HP OpenVMS Guide to System Security: OpenVMS Version 8.4 > Appendix A Assigning Privileges
This system service lets a process change its access mode to executive mode, execute a specified routine, and then return to the access mode that was in effect before the system service was called. While in executive mode, the process is allowed to execute the Change Mode to Kernel ($CMKRNL) system service.
Grant this privilege only to users who need to gain access to protected and sensitive data structures and internal functions of the operating system. If unqualified users have unrestricted access to sensitive data structures and functions, the operating system and service to other users can be easily disrupted. Such disruptions can include failure of the system, destruction of all system and user data, and exposure of confidential information.