Data Quality Monitoring for the ATLAS trigger System during the first data taking period of the Large Hadron Collider

The first long period of data taking of the Large Hadron Collider was finished after 3 years of work in February 2013. The increase of the instantaneous luminosity by more than six orders of magnitude documents impressively the extraordinary success of this running period enabling the ATLAS experiment to collect very high quality data. However, to ensure a constant and reliable monitoring and data quality assessment from the trigger's point of view, a highly flexible and powerful software framework is essential, covering many different aspects. Aside from drastically changing beam conditions as e.g. increasing pile up, the monitoring frame work has to follow up immediately and in a flexible manner all developments of the TDAQ system. The TDAQ monitoring system of ATLAS covers very different aspects as rate measurements, trigger configuration and software tests, data quality assessment and handling of events where the trigger decision has failed. Especially the data quality assessment must be made coherent at the online and offline sides. To provide data at a high quality level any occurring processing failures, misbehavior of selection algorithms and data defects must be discovered immediately and resolved accordingly. We report on the successful monitoring and data quality assessment of the ATLAS trigger system. It could be ensured, that all problems where seen redundantly by the system ensuring a proper treatment during data taking. In 2011 only 3\% of all data were declared bad due to an issue in the trigger system whereas in 2012 this could be reduced to 1\%