2.1 V9 compatibility mode and recommended mode
On Application Server 11-00, functionality for which compatibility with 09-87 and earlier versions cannot be maintained has changed to support the new Java EE 7 specifications, such as Servlet 3.1 and WebSocket 1.0. For this reason, when migrating a system designed for version 09-87 or earlier to an environment that uses version 11-00 or later, some design changes are required.
Therefore, V9 compatibility mode is provided for systems where compatibility with 09-87 and earlier versions is important. The V9 compatibility mode does not use the new functionality of 11-00. On a J2EE server configured in V9 compatibility mode, operation is equivalent to 09-87, and part of the functionality discontinued in 11-00 and later versions can also be used.
Also, the mode that does not use the V9 compatibility mode is called recommended mode. In the recommended mode, you can use the new functionality of 11-00, but cannot use the functionality discontinued in 11-00 and later versions.