The online trigger monitoring at the ATLAS experiment

The ATLAS trigger and DAQ system is a complex framework that needs a constant supervision of its functionality, ensuring a fast localisation of potential problems. This includes the technical functionality of the trigger farm, the supervision of trigger rates and the permanent control of the data quality of selected events. Therefore diagnosis must be ultimately reliable which and many complementary controlling processes are essential to recognize possible problems or irregularities. Next to the validation of the purely technical functionality, a constant supervision of the physical quality of selected data in real time is established. This is based on analyses of physically motivated quantities provided by histograms. The results using online information of the trigger process and for the standard offline reconstruction of events are then saved for further data analysis. Periods with bad trigger conditions or problematic detector performances can then be identified and excluded from the data analysis. The developed software has been used successfully in the ATLAS control room and with the standard reconstruction of events and is today a constant part of the data taking and trigger process at ATLAS. During summer and fall 2008 ATLAS data taking with cosmics as well as beam data the developed software tools has been proved to be reliable