Software process analysis and improvement relies heavily on empirical research. Em-pirical research requires measurement, experimentation, and modeling. However, what-ever evidence is gained via empirical research is strongly context dependent. Thus, it is hard to combine results and capitalize upon them for the purpose of improvement in evolving development environments. The process simulation model GENSIM 2.0, ad-dresses these challenges. GENSIM 2.0 is a generic process simulation tool representing V-model type software development processes. Compared to existing process simula-tion models in the literature, the novelty of GENSIM 2.0 is twofold. Firstly, its model structure is customizable to organization-specific processes. This is achieved by using a limited set of generic structures (macro-patterns). Secondly, its model parameters can be easily calibrated to available empirical data and expert knowledge. This is achieved by making the internal model structures explicit and by providing guidance on how to cali-brate model parameters. This article outlines the structure of GENSIM 2.0, gives exam-ples on how to calibrate the model to available empirical data, and demonstrates its use-fulness through two application scenarios The first scenario illustrates how GENSIM 2.0 helps finding effective combinations of verification and validation techniques under given time and effort constraints. The second scenario shows how the simulator sup-ports finding the best combination of alternative verification techniques.