EMS Manual

Introduction to EMS
EMS Manual—426909-005
1-4
EMS Communications in the DSM Environment
The major EMS processes (such as collectors and distributors) are controlled through
the command-response interface.
Both the EMS and command-response interfaces are based on the Subsystem
Programmatic Interface (SPI) message format. (See the SPI Programming Manual.)
The common message format for event messages and commands supported by SPI
simplifies the learning and programming tasks for programmers who deal with both
interfaces.
Because the interfaces differ in purpose and use, they also differ in certain key
characteristics:

Initiator
In the command-response interface, the management application initiates
communication with the subsystem. The operator or management application also
controls the flow of information, issuing the commands necessary to accomplish
the desired task.
In the EMS environment, the subsystem initiates communication, at least for
reporting an event to EMS. Although operators and management applications can
control how much information they request from EMS, they do not control the flow
of information into EMS itself.

Communication pattern (synchronous or asynchronous)
The command-response interface supports a dialog between a management
application and a subsystem. The management application starts a synchronous
session with a subsystem by opening the appropriate subsystem process and
Figure 1-2. EMS and Command-Response Interfaces
Event
Messages
Event
Messages
Event
Messages
Event
Messages
Command
Response
Distributors
Subsystems
Management
Applications
Log
files
Collectors
VST005.vsd