A polled alert is generated when the scheduled evaluation of a monitored resource detects an error or other condition in the resource. Polled alerts generally require threshold values to be defined so that a resource's performance can be tracked in response to these parameters. For example, threshold values can include defining criteria such as a performance level that is lower or higher than a given number, or identifying the age of a file being older than a particular time (that is, minutes, hours, days, and so forth). Threshold values give you the flexibility to refine rule conditions based on the particular performance values you choose for a resource.
