A common event flag cluster is a set of 32 event flags that
enable cooperating processes to post event notifications to each
other.
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.
Naming
Rules The name of the object is whatever character string was supplied
as an argument to the Associate Common Event Flag Cluster system
service ($ASCEFC). Remember that common event flag cluster names
are qualified by your UIC group number.
Types
of Access The common event flag cluster class supports the following
types of access:
Associate
Gives a process the right
to establish an association with the named cluster so the process
can access event flags.
Delete
Gives a process the right
to mark a permanent event flag cluster for deletion with the Delete
Common Event Flag Cluster ($DLCEFC) system service. The actual deletion
occurs once all processes disassociate from the cluster.
Control
Gives you the right to modify the protection
elements of the common event flag cluster.
Template
Profile 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.
Template Name
Owner UIC
Protection Code
DEFAULT
[0,0]
S:AD,O:AD,G:A,W
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.
Privilege
Requirements Creation of a permanent common event flag cluster requires
the PRMCEB privilege. This privilege also grants delete access for
permanent clusters.
Kinds of Auditing Performed The system can audit the following types of events:
Event Audited
When Audit Occurs
Creation
When the first process to
associate with a particular cluster calls $ASCEFC
Access
Whenever subsequent callers
to $ASCEFC associate with the cluster
Deaccess
When a process calls $DACEFC
or associates with another cluster or at image rundown
Deletion
When the process calls $DLCEFC
Permanence
of the Object A common event flag cluster and its security profile need
to be reset each time a system starts up.
HP OpenVMS Guide to System Security
Security for the User
