In general, performance issues can be categorized into five areas:
Application
CPU
Memory
Disk
Network
A bottleneck in any one area can often affect other areas as well; therefore, it is a good idea to understand each of these topics. By understanding how each of these resources is accessed and interacts, you will be able to find the root cause of issues that consume multiple resources.
Since the issue being reported did not include any details of the performance issue, we will explore and learn about each of these areas. Once complete, we will look at the data collected and look at historical statistics to determine whether the performance is as expected or whether the system performance really is degraded.