A hung Web server might be automatically restarted, a nearly full disk might have temporary files automatically cleaned off of it, or a flaky machine might be automatically rebooted. Automatically correcting as many problems as possible ensures minimum down time, and reduces the need for human intervention. Note that for most corrective actions to be taken, some element of the Web server monitor must be running on the target machine. Collecting and Using Historical Data Historical data allow the correlation of several sets of monitor readings, which may lead to a quicker diagnosis of problems. For example, if the CPU utilization of the Web server is very high, then failures to retrieve URLs during that period of time may be related to Web server overload rather than the failure of a component.
Preventative maintenance is one use of historical data.
If a disk space usage monitor indicates a disk is filling up, steps can be taken to determine the root cause well before the problem becomes critical. Cyclical patterns of usage may also be revealed. A nightly maintenance process might create temporary files that bring the disk perilously close to capacity, and then delete those files before anyone notices. Historical data can be used for capacity planning. By looking at summary reports for recent weeks and months, the trends can be used to estimate future needs.