The configuration system of the ATLAS trigger

The ATLAS detector at CERN’s LHC will be exposed to proton-proton collisions at a rate of 40 MHz. To reduce the data rate, only potentially interesting events are selected by a three-level trigger system. The first level is implemented in firmware, reducing the data output rate to about 100 kHz. The second and third levels are software triggers with an output rate of about 200 Hz. A system has been designed and implemented that hosts and records the configuration of all three trigger levels at a centrally maintained location. This system consistently provides configuration information to the online trigger for the purpose of data taking as well as to the offline trigger simulation. The use of relational database technology provides means of flexible information browsing, easy information distribution across the ATLAS reconstruction sites and reliable recording of the trigger configuration history over the lifetime of the experiment. The functionality of this design has been demonstrated in dedicated configuration tests of the ATLAS level-1 Central Trigger and of a 600-node software trigger computing farm. We present the current status of the system and its readiness for data taking. We put emphasis on the multiple use of the trigger configuration for data-taking, Monte-Carlo simulation and trigger validation.