[en] A Plant-wide and systematic Aging and Plant Life Management is essential for the safe operation and/or availability of nuclear power plants. The Aging Management (AM) has the objective to monitor and control degradation effects for safety relevant Systems, Structures and Components (SSCs) which may compromise safety functions of the plant. The Plant Life Management (PLM) methodology also includes aging surveillance for availability relevant SSCs. AM and PLM cover mechanical components, electrical and I and C systems and civil structures All Aging and Plant Life Management rules call for a comprehensive approach, requiring the systematic collection of various aging and safety relevant data on a plant-wide basis. This data needs to be serviced and periodically evaluated. Due to the complexity of the process, this activity needs to be supported by a qualified software tool for the management of aging relevant data and associated documents (approx. 30 000 SSCs). In order to support the power plant operators AREVA NP has developed the software tool COMSY. The COMSY software with its integrated AM modules enables the design and setup of a knowledge-based power plant model compatible to the requirements of international and national rules (e.g. IAEA Safety Guide NS-G-2.12, KTA 1403). In this process, a key task is to identify and monitor degradation mechanisms. For this purpose the COMSY tool provides prognosis and trending functions, which are based on more than 30 years of experience in the evaluation of degradation effects and numerous experimental studies. Since 1998 COMSY has been applied successfully in more than fifty reactor units in this field. The current version 3.0 was revised completely and offers additional AM functions. All aging-relevant component data are compiled and allocated via an integrated power plant model. Owing to existing interfaces to other software solutions and flexible import functions, COMSY is highly compatible with already existing data bases in the plant. (author)