Business process optimisation is a strategic activity in organisations because of its potential to increase profit margins and reduce operational costs. One of the main challenges in this context is concerned with the problem of optimising the allocation and sharing of resources. In this work, processes are described using the BPMN notation extended with an explicit description of execution time and resources associated with tasks, and can be concurrently executed multiple times. First, a simulation-based approach for computing certain metrics of interest, such as average execution time or resource usage, is presented. This approach applies off-line and is static in the sense that the number of resources does not evolve over the time of the simulation. In a second step, an alternative approach is presented, which works online, thus requiring the instrumentation of an existing platform for retrieving information of interest during the processes' execution. This second approach is dynamic because the number of resource replicas is updated over the time of the execution. This paper aims at stressing pros and cons of both approaches, and at showing how they complement each other.