The edition manager supports only compatible application upgrades
for edition rollout. This means that interruption-free upgrade is only for
editions that have backward compatibility. Editions with incompatible changes
can be deployed, but require the concurrent activation pattern and use of
routing rules to separate request traffic between users of the former edition
and users of the current edition. With concurrent activation, you can host
multiple editions of the same application simultaneously, with each edition
supporting a distinct, non-intersecting set of users. However, concurrent
activation does not provide interruption-free upgrade.
The following compatibility issues must be considered when you deploy editions:
- Application interfaces or semantics: If changes to existing interfaces,
including modification or removal of an existing interface will break existing
users of the application. Likewise, a change to the semantic behavior of an
interface might also break existing users, for example, if an interface formerly
allowed a parameter to be null and changes to require that the same parameter
is non-null. Changes that impact existing clients are not considered to be
backward compatible and, therefore, not amenable to interruption-free upgrade.
If impact to existing clients is not an issue, the WebSphere Application Server
rollout update can be used. For more information, see the WebSphere Application Server Information Center
- Hypertext transaction protocol (HTTP) session state: If the HTTP
session state is persisted or replicated, application changes that add or
change the data types stored in session also represent incompatible change.
The current edition might be unable to use the session state created by a
former edition.
- Web content caching: If a new application edition includes changed
static web content and you are using the WebSphere Extended Deployment on-demand
Routers (ODR) to cache content, you might need to flush the cache as part
of the edition rollout. Use the cache monitor utility to perform this task
manually. Documentation for this utility can be found at: WebSphere Application Server Information Center