Historically focused tools periodically collect data and then allow you to "look back in time," as they say. Examples of historical tools are Statspack and AWR. Historical tools are wonderful for analyzing a problem after it happened (like while you slept last night), when multiple problems need to be analyzed, or if you need to reference a past situation (this occurs more often than people think). Historical tools usually provide trending and graphing capabilities, which are especially helpful in communicating with nontechnical people.

Historical product vendors have a very technically challenging problem. They want to gather as much data as possible and as frequently as possible. However, vendors know the more frequently they gather data and the more data they gather, the more their collection activities will impact the system. This is one reason why good historical products seem expensive. In Chapter 5, which covers Oracle performance diagnosis, I will address data-collection challenges.

Firefighting vendor products shine when they blend interactive and historical capabilities. Regardless of the tools you use, ensure you have both interactive capabilities and historical capabilities. Always have your tools installed, running, and ready.