The DZERO Level 3 DAQ System: Operation and Upgrades

The D Level 3 data acquisition system for Run II of the Tevatron has been reliably operating since May 2002. Designed to handle average event sizes of 250 kilobytes at a rate of 1 kHz, the system has been upgraded to be able to process more events, doubling its typical output rate from 50 Hz to 100 Hz, while coping with higher event sizes at the beginning of high luminosity collider stores. The system routes and transfers event fragments from 63 VME crates to any of approximately 320 processing nodes. The addition of more farm nodes, the performance of the components, and the running experience are described here.