CMS Data preparation for Run II

The LHC Run II will bring new challanges, mainly due to the higher number of interactions per beam crossing andthe reduced time spacing between the crossings. In order to be ready for the beginning of the run, the CMS Collaborationis evolving the infrastructures, developed during Run I to monitor the data quality, to validate the progress on the detector simulation, event reconstruction , physics object definition and to handle large scale production of simulateddata samples. This contribution covers the development and operational aspects put in place for Run I and describeshow the experience gained is guiding the planning for Run III