Oracle E-Business Suite provides several types of logs. One of the tools you can use is the Logging Framework, which allows you to collect and view log messages in Oracle Applications Manager. The Logging Framework collects debug messages, errors, and alerts.
A Global Diagnostics Trace can help you diagnose issues if errors occur when users click a button or select an option. It's a targeted trace that can be run per user, thereby minimizing the impact on the overall performance of your environment. This kind of trace is also known as an FND Diagnostics Trace or Oracle Applications Logging.
You can find a quick summary of steps to enable a Global Diagnostics trace here:
There's lots more information about more-powerful logging options in the following manuals: