Interoperating multiple application server versions

Read Overview of migration, coexistence, and interoperability and Premigration considerations. For resources to help you plan and perform your migration, visit Knowledge Collection: Migration planning for WebSphere Application Server.

Interoperability applies to WebSphere administrative actions, administrative communication and to application client requests. WebSphere Application Server Version 8.5 is generally interoperable with WebSphere Application Server Version 6.1 and later. However, there are specific requirements to address for each version. In general, you should apply the latest fix level to support interoperability. If this is not possible, then the following interim fixes can be used to support your environment.

You can upgrade a portion of the nodes in a cell to WebSphere Application Server Version 8.5 while leaving others at the older release level. This means that, for a period of time, you might be administering servers that are at the current release and servers that are running the newer release in the same cell.

For web application clients, interoperability is provided by employing the HTTP server plug-in at the highest version of all of the application servers in the cell. For example, a cell comprised of WebSphere Application Server Version 7.0 and Version 6.1 application servers would use a supported HTTP server with a Version 7.0 plug-in. See Technote Web server plug-in policy for WebSphere Application Server for more information.