Optimize Distributed Workload - Expert Oracle RAC Performance Diagnostics and Tuning - page 493

FAN Events
When a state change occurs on a cluster or node or instance in a RAC environment, the Event manager triggers an
event propagated by the ONS to the client machines. Such events that communicate state changes are termed as FAN
events and consist of a predefined structure. Every FAN event consists of a header and payload information sent in
name-value pairs from the origination to the respective targets participating in the framework. The name-value pair
describes the actual name, type, and nature of the event. On receipt of this information, the recipient or the target
application will take appropriate steps, such as routing the connection to another instance and so forth, based on the
type of notification received.
Oracle supports two types of events:

1.

Service event: Service events are application events and contain state changes that would
only affect clients that use the service. Normally such events only indicate database,
instance level, and application service failures.

2.

System events. System events are more of a global nature and represent events such as node
and communication failures. Such events affect all services supported on the specific system,
for example, cluster membership changes, such as a node leaving or joining the cluster.

3.

Both of the preceding types of events contain the following structure:

<Event_Type> VERSION=<n.n> service=<serviceName.dbDomainName>
[database=<db_unique_name> [instance=<instance_name>]] [host=<hostname>]
status=<Event_Status> reason=<Event_Reason>[card=<n>] timestamp=<eventDate>
<eventTime>
The various attributes used in the event and the descriptions can be found in Table 15-1 .

Table 15-1. ONS Event Descriptions

Event Identifier Description

<Event_Type> There are several types of events that belong to either the service type or system type of event:

SERVICE

Indicates it's a primary application service event, e.g., database service.

SERVICEMEMBER Application service on a specific instance event.

DATABASE Indicates it's an Oracle database event.

INSTANCE Indicates it's an Oracle instance event.

NODE Belongs to the system type event and indicates an Oracle cluster

node event.

VERSION This is an event payload version. This normally reflects the version of the database or

Clusterware. When an environment supports several databases and they have different
Clusterware versions, the payload version would help determine what actions to take
depending on the features supported by the version.

SERVICE

Name of the database service.

DATABASE Unique name of the RAC database for which the event is being raised. The name matches the

DB_UNIQUE_NAME , which defaults to DB_NAME parameter.

( continued )