1. A computer-implemented method for operating two versions of an application program while in the process of upgrading a computing environment including one or more groups of mobile clients, the method comprising: operating a starting-version application accessible to one or more starting-version mobile clients; operating a target-version application accessible to one or more target-version mobile clients; sending from the starting-version application a data exchange message including one or more starting-version data modifications associated with the data exchange message; and storing the one or more starting-version data modifications associated with the data exchange message in association with the target-version application such that the one or more starting-version data modifications are available to one of the one or more target-version mobile clients.