So is there any IO subsystem bottleneck? Clearly, the IO subsystem capacity has exceeded Oracle's IO read requirements, which means there is not an IO bottleneck. But this in no way implies there is not a problem. If users are unsatisfied with application performance, you will probably be able to discover Oracle-focused, operating system-focused, and application-focused solutions, such as the following:

* Oracle focused: If the desired block had been found in the Oracle buffer cache, Oracle would not have asked the operating system for the block. Therefore, a larger Oracle buffer cache would reduce the likelihood of a db file scattered read. Of course, there needs to be both memory available and CPU available to manage the increased buffer cache. Other possibilities are using the keep or recycle pools, or other Oracle instance-focused solutions to increase the likelihood of the block being found in Oracle's buffer cache.

* Operating system-focused: From an operating system perspective, there is a high likelihood the CPU subsystem is the bottleneck. This is very common when the top event is IO read-related yet the operating system satisfies the request in only a couple of milliseconds. If the IO subsystem is part of the database server (think small Linux server), this is likely. For large systems with a separate IO subsystem, this is less likely. If there is a CPU bottleneck, look for ways to increase the CPU capacity.