The sar command in Linux gathers, reports, or stores system activity information and is used to log and analyze a range of system activity data. When dealing with performance issues, sar also allows for a retrospective study of load values for various sub-systems (CPUs, memory, disks, interrupts, network interfaces, and so on). The sampled workload is deemed CPU-bound if CPU usage is close to 100%.
The sar command’s log files are stored by default in the /var/log/sa/sadd file, with the dd argument indicating the current day.