Abstract
As the computational and data handling requirements of large scientific collaborations grow, Grid computing is rapidly emerging as a feasible solution to these requirements. Optimising the use of Grid resources is crucial, and to evaluate potential optimisation strategies it is important to simulate them as realistically as possible before they are used on real Grids. We have developed the Grid simulator Optorsim and used it to test several optimisation strategies using a set of performance metrics. In this paper we consider the effects of several scheduling and replica optimisation strategies and base our simulation environmnet on the UK Grid and Particle Physics (GridPP).