Availability Guide for Application Design

Instrumenting an Application for Availability
Availability Guide for Application Design—525637-004
8-24
The Subsystem Programmatic Interface (SPI)
If the command message is in response to an event—as is typical when an automated
operator is used—then some of the command message contents are derived from the
event message as shown in Figure 8-7 on page 8-24. Thus, the subsystem identifier is
copied from the event message, the command type and object type are derived from
the event number, and the object name is derived from the event subject. As already
indicated under EMS Messages on page 8-20, it is important that the information in the
event message is in the proper format for use by the corresponding command.
Examples of Command Messages
The following examples show the kinds of operations that you might carry out on an
application using command messages:
•
Switch to a new server class.
You might issue such a command in response to repeated failures in the current
server class or to achieve application upgrade.
•
Obtain new configuration information.
You might use this information to diagnose a fault or to establish what response to
make following a reported problem.
•
Stop or start processing a specific type of interprocess message.
You might issue this kind of command to diagnose a fault.
•
Suspend processing for a specified number of seconds.
You might issue this command to temporarily reduce the load on an overused
resource.
•
Switch to use an alternate file.
Figure 8-7. Transposing Event Data Into Command Data
Subsystem
Identifier
Event
Number
Event
Subject
Other Event
Information
Object
Name
Other Command
Information
Command
Type
Object
Type
VST707.vdd
Subsystem
Identifier