Which feature will support this requirement?

D is the correct answer!

Note: Do not configure Transparent Application Failover (TAF) with
Fast Connection Failover for JDBC clients as TAF processing can
interfere with FAN ONS processing.

Configuring Clients for High Availability

There are three central elements to consider when automating failover for application
clients:
■ First, clients that are connected at the time of failure must be quickly and
automatically notified that a failure has occurred to avoid waiting for TCP/IP
network time-outs before attempting to connect to the new database instance
(such time-outs range anywhere from eight minutes to two hours, depending on
operating system). Oracle RAC configurations use Fast Application Notification
(FAN) to notify JDBC clients, OCI clients, and ODP.NET clients. FAN event
notifications and callouts enable automatic and fast redirection of clients after a
site failure.
■ The second central element of client failover, is the redirection of new incoming
requests to the new instance after a failure has occurred, which can be
implemented using application services. When you create application services in
an Oracle RAC database, if an instance to which you have assigned a service
becomes unavailable, then the service is already available at another Oracle RAC
instance or Oracle RAC relocates the service to an available instance of the
database. Applications need only provide the name of the dynamic database
service in their connect strings–there is no need to specify an instance name
because, using listener cross registration, SCAN listeners and other remote
listeners in the cluster are aware of which instances are currently providing a
service when a connection request comes in.
■ The third central element is masking the outage from the client and the
application. Masking outages of the database session is a complex task for
application development and, therefore, errors and timeouts are often exposed to
the client. Application Continuity attempts to mask outages from applications by
replaying incomplete application requests after unplanned and planned outages.

For applications that are unable to take advantage of Application Continuity, two
additional features are available: Transparent Application Failover (TAF) for OCI
based applications and Transaction Guard. Transaction Guard enables applications to
build their own masking of outages by knowing the outcome of the last in-flight
transaction.

Configuring JDBC Clients for High Availability
…
Without Fast Connection Failover, if a node or network goes down and the application
attempts to connect to that instance, then the connection request might hang for
several minutes waiting for the TCP time out to be reached. If you chose not to use a
connection pool with the integrated FCF feature, then your application can still be
notified of Oracle RAC high availability events by configuring the Connection Failure
Notification feature.

ANSWER A

TAF is a database session-level connection failover mechanism: it works via the OCI interface only so applies to applications using thick JDBC drivers and those using the OCI libraries; TAF is runtime feature of OCI driver – it enables application automatically ; You can use both TAF and FAN at the same time, or both TAF and FCF(both JDBC thin and JDBC OCI drivers are supported), it depends on what you want to achieve with it; FCF is a feature of Oracle clients that are integrated to receive FAN events and abort inflight transactions, clean up connections when a down event is received as well as create new connections when a up event is received. Tomcat or JBOSS can take advantage of FCF if the Oracle connection pool is used underneath. This can be either UCP (Universal Connection Pool for JAVA) or ICC (JDBC Implicit Connection Cache). UCP is recommended as ICC will be deprecated in a future release.

##Thick JDBC## – url=” jdbc:oracle:oci@service_name”