Documentation has been mentioned briefly numerous times in both this chapter and in Chapter 1, but it needs to be mentioned again in its own right. Without good documentation, a data center will not be able to function smoothly. If the operator responsible for the day-to-day monitoring does not know the system configuration and its purpose, how can he or she know that there is problem if a blip occurs in Performance Monitor? Are there baseline performance benchmarks to compare against? Baselining and monitoring are discussed in Chapter 15, Monitoring for High Availability.
The document most data centers will have is what is referred to as a run book . A run book is a collection of documentsfrom system configurations to disaster recovery plans and everything in betweenthat will become the primary resource for system administrators and developers alike. The run book needs to be kept up to date with any changes, and all changes should stay in the run book so anyone who comes into contact with it will understand the history. Chapter 12, Disaster Recovery Techniques for Microsoft SQL Server, discusses run books in more detail, including how to create one.