Using application profiling with 5.x compatibility mode or in a clustered environment with mixed WebSphere Application Server product versions and mixed platforms can affect its behavior in different ways.
Application profiling supports forward compatibility. Application profiles created in previous versions of WebSphere Application Server (Enterprise Edition 5.0 or WebSphere Business Integration Server Foundation 5.1) can only run in WebSphere Application Server Version 6 or later if the Application Profiling 5.x Compatibility Mode attribute is turned on. If the 5.x Compatibility Mode attribute is off, Version 5 application profiles might display unexpected behavior.
Similarly, application profiles that you create using the latest version of WebSphere Application Server are not compatible with Version 5 or earlier versions. Even applications configured with application profiles run on Version 6.x servers with the Application Profiling 5.x Compatibility Mode attribute turned on cannot interact with applications configured with profiles run on Version 5 servers.
For a Version 6.x client to interact with applications run under the Application Profiling 5.x Compatibility Mode, you must set the appprofileCompatibility system property to true in the client process. You can do this by specifying the -CCDappprofileCompatibility=true option when invoking the launchClient command.
If you use WebSphere Application Server Enterprise Edition 5.0.2, you must apply WebSphere Application Server Version 5 service pack 7 or later service pack to enable Application Profiling interoperability.