Abstract
In this contribution, the model of shared ATLAS Tier-2 and Tier-3 facilities is explained. Data taking in ATLAS has been going on for more than two years. The Tier-2 and Tier-3 facility setup, how do we get the data, how do we enable at the same time Grid and local data access, how Tier-2 and Tier-3 activities affect the cluster differently and process of hundreds of millions of events, are described. Finally, an example of how a real physics analysis is working at these sites is shown, and this is a good occasion to see if we have developed all the Grid tools necessary for the ATLAS Distributed Computing community, and in case we do not, to try to fix it, in order to be ready for the foreseen increase in ATLAS activity in the next years.