Distributed Name Service (DNS) Management Programming Manual

DNS Subsystem Architecture
Introduction
46958 Tandem Computers Incorporated 1–7
Event-Management
Interface
Event messages from DNS are made available to management applications by the
Event Management Service (EMS). EMS collects, logs, and distributes event messages
that provide information to help you monitor the network environment, analyze
failures, and recognize and handle critical problems.
Figure 1-4 illustrates the event-management interface to DNS and related subsystems.
The following steps summarize the activities shown in the figure:
1. An event occurs in the DNS subsystem environment.
2. A DNS subsystem process (name manager, name exporter, or DNSCOM ) reports
the event by sending an event message, formatted as an SPI buffer, directly to the
local EMS collector.
3. The collector stores the event message in a disk file called the event log.
4. If a forwarding distributor is present, this distributor forwards the event message
to a collector on a remote node. The remote collector stores the message in an
event log on its own node, so that the message exists on both nodes. (This feature
does not appear in the figure.)
5. An application optionally installs an EMS filter specifying the selection of event
messages it wants to receive. DNS does not generate many events, so using filters
is not as necessary with DNS as it is with other subsystems. If no filter is installed,
all event messages will be delivered to the application.
6. The application opens an EMS consumer distributor and requests an event
message.
7. The distributor reads the log and returns to the application the next event message
that satisfies the conditions of the filter.
8. The application either presents the message to the operator or takes action itself.
For information about when DNS generates event messages, see “Event Messages”
later in this section. Section 6 describes the contents and meaning of all DNS event
messages.