Data Bookkeeping Service 3 - A new event data catalog for CMS

The Data Bookkeeping Service (DBS) provides an event data catalog for Monte Carlo and recorded data of the Compact Muon Solenoid (CMS) Experiment at the Large Hadron Collider (LHC) at CERN, Geneva. It contains all the necessary information used for tracking datasets, like their processing history and associations between runs, files and datasets, on a large scale of about $10^5$ datasets and more than $10^7$ files. The DBS is widely used within CMS, since all kind of data-processing like Monte Carlo production, processing of recorded event data as well as physics analysis done by the user, are relying on the information stored in DBS.