Edition compatibility

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. To perform this task manually, read about the cache monitor.