Advanced Features of ADF - Oracle ADF 11gR2 Development Beginner's Guide - page 261

More informaion can be found at the following link:

http://docs.oracle.com/cd/E35521_01/web.111230/e16182/bcadvvo.
htm#sm0331

Application module state management

Since an applicaion module is responsible for the transacion management of an applicaion,
it includes some of the seings and coniguraions for high availability and to maintain the
state of the applicaion. High availability is a concept in which the state of an applicaion is
maintained even when the handshake between servers occurs in a clustered environment.
In this context, a handshake means that when a server goes down, the clustered server gets
another server up and running to maintain the state of the applicaion.

For example, a user connects to a website that is hosted on a clustered server and gets
connected to Server1 of that cluster. The user starts creaing a new record at the same
ime that Server1 goes down for maintenance. At such a ime, the user data should not
be lost, and the user should be allowed to coninue with the creaion of the record. For
this to happen, the state of the applicaion has to be maintained so that the state of the
applicaion is transferred from Server1 to Server2, and the user will not see the change
in the state of the applicaion. The following screenshot explains this:

Browser

Server1
is up

Server1
is down

Application

1 1

User

2 3

Server3 is up

Server2 is up

Passivaion is done in the server to store the state of the applicaion, and the passivaion
state can be stored in a lat ile or a database. Acivaion reloads the state of the applicaion
at the point where it was let. The two APIs that are helpful in the applicaion module for
high availability are assivateState() and activateState() .The failover feature is
enabled by seing the value of jbo.dofailover to true in the applicaion module.
With this seing, the passivaion state will occur at the end of every request.