1. A method for upgrading the software in a system comprising several application modules running in parallell, one or more of the modules holding configuration data and/or transaction data which must survive the upgrade operation, comprising the steps of: a) the new software is installed on the system and activated, b) all modules are ordered to save their configuration and/or transaction data, c) all modules are stopped, d) all modules are restarted from the new software version, e) any module which need to convert the configuration and/or transaction data in order to comply with the new software version will load said data from the database and define an upgrade module, f) said upgrade module will read said data, convert the data into the required format, and save the converted data.