In this case study, management is concerned about periodic and increasingly intense periods of performance slowdowns. Several key business processes are being affected, as well as general application performance. Management wants you to diagnose the system, recommend solutions, work with the various teams to ensure the solutions are implemented, and then confirm performance is back to previously accepted levels.

Using 3-circle analysis, you focus on each of the three circles, and then establish their interrelationships. Where you find overlap or where the relationship is the strongest, that's the bottleneck or the area that needs your immediate attention.

Suppose an Oracle response-time analysis, introduced in the "Oracle Response-Time Analysis" section later in this chapter, shows Oracle processes are primarily waiting for multiple IO block requests. I like to call this physical IO, but really the blocks are simply not in Oracle's buffer cache and reside somewhere else. The terms block reads, block requests, block gets, and disk reads are also commonly used. On the other hand, a buffer get is an attempt to retrieve a block buffered in the Oracle buffer cache. This is also commonly called logical IO, because it is not a physical IO request. It is helpful to think of blocks as residing outside Oracle's buffer cache and on disk, and to think of buffers as residing inside the Oracle buffer cache. The Oracle response-time analysis shows these IO requests take an average of 22 milliseconds (ms) to complete, and the Oracle server and background processes are consuming about 30% of the available operating system CPU.