Abstract. One of the reasons for attending to agent technology is the evergrowing complexity of information systems and the increasing difficulty to foresee and plan for all potentially arising situations. Unfortunately, some pressing issues in practical applications still remain outside the focus of agent research. Chief among them is robustness in environments that are prone to disturbances, failures or uncontrolled interactions. In our research effort, we provide a middleware, based on database transactions, that formally guarantees robustness of execution of agent actions and automates many standard actions carried out in case of disturbances. We built a simulator to test the scalability of the proposed middleware. The simulator also gives us a better understanding of the behavior of the various planning strategies reflected by the transaction trees executed by the middleware and is a valuable tool for evaluating the performance of any multi-agent system before its actual deploymen...