DTrace enables you to aggregate data gathered by the probes. For example, if you wanted to know the number of system calls by user ID, you would not necessarily care about the data collected at each system call. You simply want to see a table of user IDs and system calls. Without aggregation, you would have postprocessed the data gathered at each system call by using a tool such as awk or perl. For more information, see the awk(1) and perl(1) man pages. In DTrace, aggregation of data is a first-class operation.