The following limitation is not an issue when you upgrade from version 9.0.0 or 9.0.1 to version 9.1.0.
IBM® Endpoint Manager for Remote Control version 9.0.0 introduced new capabilities that can cause some backwards compatibility issues if the different components are not upgraded in the correct order.
This limitation applies only to environments where the gateway and broker components have been deployed. In these environments, the broker and gateway must be updated before the server or the target components. After they are upgraded, the targets and server can be upgraded in the order that best suits your environment, since there are no dependencies between them.
It is recommended to always back up any properties files as a precaution, however it must be noted that this is mandatory for the controller upgrade in this release, as any existing properties will be lost.