The ATLAS Trigger Monitoring and Operation in proton-proton collisions

With the first proton-proton collisions at $sqrt{s}=900~mathrm{GeV}$ in December 2009, the full chain of the ATLAS Trigger and Data Acquisition system could be tested under real conditions for the first time. Monitoring the performance and operation of these systems required a smooth and parallel running of many complex software tools depending on each other. They are the basis of rate measurements, data quality determination of selected objects and supervision of the system during the data taking. Based on the successful data taking experience with first collisions, the ATLAS trigger monitoring and operations performance are described.