In this paper, an algorithm (APES) to compute the acceptance probability of a global transaction in a multidatabase system is synthesized. A concurrency control algorithm (SGA) modeled by Generalized Stochastic Petri nets is also presented. Using the probabilities given by the APES algorithm, the degree of concurrency of the SGA is evaluated by a GSPN model. Finally, some examples are given to illustrate this study.