iDoctor is the best tool for doing deep dive performance investigations on IBMi. iDoctor gives you a good graphical understanding about your performance data. This can be when you are looking at Collection Services data and Job Watcher data, but also PEX (Performance Explore) data. Wait accounting will be reviewed, so you understand how IBM i can make it possible to collect performance data used for deep diving into partition and your applications.
You will see practical examples of iDoctor analyzing Collection Service data, Job Watcher data and PEX data, so you can get very deep information about bottlenecks and issues in jobs/threads that can help you solve performance problems.