Abstract
The remit of the European DataGrid (EDG) project was to develop an infrastructure that could support the intensive computational and data handling needs of widely distributed scientific communities. An important part of managing the data present in such a Grid is file replication - placing copies of files at different sites in order to reduce data access times, hence shortening job running times and improving the use of Grid resources. In the search for an optimal solution to this problem, the Grid simulator OptorSim was developed as part of the EDG project. Here, an overview of OptorSim is presented with details of its implementation, features and capabilites.