CMS data preparation for Run II

The Run II of the Large Hadron Collider will confront us with new challenges, mainly due to the higher number of interactions per bunch crossing and the reduced time distance between bunches. In order to be ready for the beginning of the run, in view of an early discovery, the CMS collaboration is currently evolving the infrastructure established during Run I to monitor the data quality, to validate the progresses on detector simulation, event reconstruction, physics objects definition, and to handle large scale production of simulated events. This contribution covers the development and operational aspects of data preparation at CMS for Run II and describes how the experience gained from Run I is serving the planning of the physics program for Run II.