This paper characterizes the production workload that highly utilizes the NCSA Origin 2000. The characterization includes the distributions of job interarrival time, requested number of processors, requested memory, requested runtime, actual runtime as a fraction of requested runtime, and the ratio of memory usage to memory request. Conditional distributions are defined as needed for generating a synthetic workload with the same characteristics, including the key correlations observed among the job parameters. Characteristics of the O2K workload that differ from previously reported production workload characteristics are also noted.