HP OpenVMS Guide to System Security: OpenVMS Version 8.4 > Chapter 12 Securing a Cluster
Clustered systems use a group number and a cluster password to both allow multiple independent clustered systems to coexist on the same extended local area network (LAN) and to prevent accidental access to a cluster by unauthorized computers. The group number uniquely identifies each cluster system on a LAN. The cluster password serves as an additional check to ensure the integrity of individual clusters on the same LAN that accidentally use identical group numbers. The password also prevents an intruder who discovers the group number from joining the cluster.
The cluster group number and password (in encrypted form) are maintained in the cluster authorization file, SYS$COMMON:[SYSEXE]CLUSTER_AUTHORIZE.DAT. This file is created during installation of the operating system if you indicate that you want to set up a local area or mixed interconnect cluster. The installation procedure then prompts you for the cluster group number and password.
Under normal conditions, you need not alter records in the CLUSTER_AUTHORIZE.DAT file interactively. However, if you suspect a security breach, you may want to change the cluster password. In that case, you use SYSMAN to make the change. The file is accessible only to users with the SYSPRV privilege. Note that if you change either the group number or the password, you must reboot the entire cluster.