Figure 7-17. How IMU nodes are used instead of traditional undo segments, as well as the various key components (data buffer, IMU nodes, undo buffer, redo buffer, and online redo log) change as a transaction progresses

Although multiple bugs were logged when IMU was first introduced, it now works wonderfully. But the real question and our chief concern in this book is this: Does it improve response time? This is especially important for applications with heavy consistent read activity, since these use undo extensively.

I decided to perform an experiment. Before I share the results, I'll explain how I set up the experiment. Take a deep breath, and continue.