Most computer users become aware of the inadequacies of their computer when it appears to slow down.
On-line response time may be getting longer between transactions or it may be moving to the limit of tolerance. Batch jobs may be taking more time than they used to or maybe nighttime runs interfere with the daytime on-line work. There are times when these situations happen quickly, but most often, it is a gradual process. The things that cause a computer system to be degraded are not always a lack of processor power. Memory, disk, and data communications need to be considered.