Adding the O/S Metrics
Oracle does a pretty good job of gathering performance statistics and metrics, but sometimes, especially when you encounter a bug situation, Oracle can miss the mark. It also has issues collecting and reporting low-level I/O data, such as that provided at the O/S level. In these situations, we turn to iostat, an O/S level utility that reports both the wait time and service time for I/O requests, something that Oracle cannot do.
The iostat utility can produce two types of reports, one for CPU utilization and the other for device utilization. When iostat is called without parameters, these two types are combined into a single output block, and an example of that follows.
[celladmin@myexa1cel04 ∼]$ iostatLinux 2.6.32-400.11.1.el5uek ...