EMS Manual

Reporting Events
EMS Manual—426909-005
8-3
Task 1.2: Decide Which Reported Events Are
Critical or Action Events
detect this situation). For example, a subsystem that performs retries when a
failure occurs should send one event message after exhausting the retry count,
rather than send one event message for each retry attempt. You might discover
more subtle cases where it would be appropriate to condense redundant events
into a single event message or to report only the first occurrence of an event.

Report each event in only one event message. That is, each event message
should be self-contained. If multiple messages are used to report the same event,
there is no way to ensure that an application would retrieve all of them in order with
no intervening messages.
Task 1.2: Decide Which Reported Events Are Critical or Action
Events
Determine if any of the events you report to EMS should be treated as critical or action
events. ViewPoint recognizes these two special classes of events as being different
from normal events.
Critical Events
Critical events should be events that indicate significant loss of or damage to your
subsystem’s environment.
Critical events are denoted by a special token, called ZEMS-TKN-EMPHASIS. If the
emphasis token has the value TRUE, ViewPoint highlights the message in its display.
Choose your critical events carefully. If most events are displayed as critical events, the
concept loses its significance.
Designate these event classes as critical:

Potential or actual loss of data

Loss of a major subsystem function

Loss of fault-tolerance capability, such as a redundant resource or a failure-
recovery function

Loss of subsystem integrity (an unrecoverable internal error)
Action Events
Action events arise when a subsystem determines that a problem cannot be resolved
without operator intervention, such as needing a tape mounted.
Follow these guidelines for choosing action events:

Report an action event when your subsystem cannot continue its work until and
unless the operator takes some action. Subsystems that control mechanical
peripherals often have to resort to reporting action events, such as when tapes