The application edition manager supports only compatible application
upgrades for edition roll out, which means that interruption-free upgrade
is only for editions that are compatible with previous editions. When you
deploy editions with incompatible changes, the editions 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 might not provide interruption-free upgrade.
Consider the following compatibility issues when you deploy editions:
- Application interfaces or semantics: Active users who are currently
using the application might be affected if application interfaces or semantics
are changed between editions when a roll out is attempted. Examples of changes
include those to existing interfaces, including modification or removal of
an existing interface. Also, a change to the semantic behavior of an interface
might also affect active users. For example, if an interface formerly allowed
a parameter to be null, then the change requires that the same parameter is
non-null. Changes that impact existing clients are not considered to be backward
compatible and cannot be a part of an interruption-free upgrade. If impact
to existing clients is not an issue, then use the WebSphere® Application Server roll
out update.
- Hypertext transfer protocol (HTTP) session state: If the HTTP session
state is persisted or replicated, then application changes that add or change
the data types that are 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 on demand router (ODR) to cache content,
then you might need to flush the cache as part of the edition roll out. For
more information, see the topic in
the WebSphere Application
Server information center to perform this task manually.