14.5 Updating applications

WAS has features that allow applications to be updated and restarted at a fine-grained level. It is possible to update only parts of an application or module and only the necessary parts are restarted. You can:

-	Replace an entire application (.ear file).

-	Replace, add, or remove a single module (.war, EJB .jar, or connector .rar file).

-	Replace, add, or remove a single file.

-	Replace, add and remove multiple files by uploading a compressed file describing the actions to take.

If the application is running while being updated, WAS automatically stops the application, or only its affected components, updates the application, and restarts the application or components.

When updating an application, only the portion of the application code that changed needs to be presented to the system. The application management logic calculates the minimum actions that the system needs to execute in order to update the application. Under certain circumstances, the update can occur without stopping any portion of the running application.

WAS also has support for managing applications in a cluster for continuous availability. The action, Rollout Update, sequentially updates an application installed on multiple cluster members across a cluster. After you update an application's files or configuration, use the Rollout Update option to install the application's updated files or configuration on all cluster members of a cluster on which the application is installed.

Rollout Update does the following for each cluster member in sequence:

1. Saves the updated application configuration.

2. Stops all cluster members on a given node.

3. Updates the application on the node by synchronizing the configuration.

4. Restarts the stopped cluster members on that node.

This action updates an application on multiple cluster members while providing continuous availability of the application.

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