Oracle and Availability: Illustrated Downtime Scenarios

As you have already discovered, or perhaps are about to discover, maintaining the high-availability database is a tricky prospect. There are hundreds of possible sources of downtime hiding in the crooks and crannies of your enterprise. Many outage situations cascade into each other, where an attempt to resolve a problem creates another outage and quickly spirals further and further out of control. But almost all downtime scenarios can be prevented with careful planning or swift corrective action.

Throughout this book, we discuss numerous technologies that prevent or drastically reduce different database outages. But what are these downtime scenarios? Which possible outages can you protect yourself against? In order to illustrate the various types of situations that threaten the availability of your database, we will illustrate various database problems that can be prevented using the technologies outlined in this book. We have typically provided a worst-case scenario, but we wanted to place the high-availability technologies in Chapters 2 through 11 in a real-world context prior to exploring the configuration and administration of these technologies.

After each downtime scenario, a text box will describe which piece of technology could be employed to prevent the outage, or to recover from it quickly. If you are not interested in reading through the situations, you can skim through this chapter and just look for the boxes. The boxes provide a road map to the available technologies that are discussed in the rest of this book.