When you deploy an application you can also specify

When you deploy an application, you can also specify an edition description next to the
edition name, which gives you the ability to store more information.
Non-destructive update
The existing application installation and update functions in Network Deployment are
destructive. That is, they replace the old instance of the application with a new instance.
Installing an application edition is
non-destructive
. You can install any number of application
editions and keep them in the system management repository.
State
Each application edition that is deployed has a
state
that identifies the status of the
application edition. Each application edition must be in one of the following states or modes:
Active
Inactive
Validation
Because the application edition changes from one state to another, various actions occur,
such as installing, validating, activating, running a rollout, deactivating, and uninstalling. After
installing a new edition of an application, the new edition is only activated if there is not
already an active edition deployed to the same cluster. For each application and deployment
target combination, there can be at most one edition in active mode and one edition in
validation mode. An edition that is in the inactive state is not started when an application
server starts.

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WebSphere Application Server V8.5 Concepts, Planning, and Design Guide
5.6.3 Concepts
The application edition management feature provides the following capabilities:
Rollout
indicates policies that allow you to switch from one edition to another edition with
no loss of service.
Concurrent activation
where multiple editions can be concurrently active for an extended
period.
A
validation mode
to send selective traffic to verify the correct operation.
Rollout
Rollout activation activates one edition in place of another, ensuring an interruption-free
update in the process. Thus, all application requests are serviced during the rollout and none
are lost. This process ensures continuous application operation from the perspective of the
customers of that application. To do so, the application edition manager carefully coordinates
the activation of the edition and the routing of requests to the application.
During rollout, you make the following choices:
Soft or hard rollout
A soft rollout stops and starts only the application, whereas a hard rollout stops and starts
the application server. You might consider a hard rollout if an application must reload
native code.
Atomic or group rollout
An atomic rollout ensures that two editions do not service requests at the same time,
whereas a group rollout does not ensure this. The atomic rollout can queue requests
briefly in the ODR to ensure atomicity. A group rollout does not queue requests.