EMS Manual

EMS Components and Architecture
EMS Manual—426909-005
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Special Kinds of Event Messages
Subsystems typically identify these events as critical:

Potential or actual loss of data

Loss of a major subsystem function

Loss of a fault-tolerance capability, such as a redundant resource or failure-
recovery function

Loss of subsystem integrity (for example, an unrecoverable internal error in a
subsystem)
To indicate a critical event, the subsystem assigns the value TRUE to the ZEMS-TKN-
EMPHASIS token. For a description of EMS tokens and conventions, see Section 14,
EMS Definitions.
The ViewPoint application highlights critical events in its event display. (For details, see
the ViewPoint Manual.)
Action Events
A subsystem reports an action event when a situation arises that the subsystem
cannot resolve without operator intervention. For example, a subsystem might report
an action event when it cannot proceed until a tape is mounted or a printer ribbon is
replaced.
Action events are reported in pairs of event messages. The first message, called an
action-attention message, reports the problem. The second message, called an action-
completion message, reports that the appropriate action has been taken. (In some
cases, the subsystem can directly detect that the situation has been corrected. In other
cases, the operator has to inform the subsystem of the action taken.)
Action events are designated by the presence of the ZEMS-TKN-ACTION-NEEDED
token:

The value TRUE designates an action-attention message.

The value FALSE designates an action-completion message.
Another token, ZEMS-TKN-ACTION-ID, should be included in each pair of action-
attention and action-completion messages with the same value in each message. (If
the subsystem generates the completion message, it includes the correct action ID
automatically.)
The action ID lets the operator or management application retrieving an action-
completion message identify the action-attention message to which it corresponds. For
a detailed description of EMS tokens and conventions, see Section 14, EMS
Definitions.
The ViewPoint application counts and highlights action-attention messages in its event
display, decrementing the count and dimming the message when the corresponding
action-completion message is retrieved. (For details, see the ViewPoint Manual.)