HP OpenVMS Guide to System Security: OpenVMS Version 8.4 > Chapter 5 Descriptions of Object Classes
Event flags in the cluster can be set or cleared to indicate the occurrence of an event. All event flags are contained within clusters of 32 event flags, and each process has access to four clusters (numbered 0 through 3). Two of the clusters are local to a single process. Event flag clusters 2 and 3 are called common event flag clusters and are used for interprocess synchronization. A subject may be associated with up to two common event flag clusters. Each common event flag in a cluster is referenced by an event flag number.
The name of the object is whatever character string was supplied as an argument to the Associate Common Event Flag Cluster system service ($ASCEFC). Remember that common event flag cluster names are qualified by your UIC group number.
The common event flag cluster class provides one template profile. Although the template assigns an owner UIC of [0,0], this value is only temporary. As soon as the object is created, the operating system replaces a 0 value with the value in the corresponding field of the creating process's UIC.
When the process creating the common event flag cluster supplies a prot argument to $ASCEFC that has a value of 1, then the system modifies the template so the process UIC is the owner, and the protection code denies group access.