Diagnostic tracing data provides a record of all activities that took place on the database server corresponding to the tracing levels and settings configured for the tracing session. Consequently, when reviewing the data, you must consider the settings that were in place. For example, the absence of a statement that you expected to see in a tracing session might indicate that the statement never ran, but it might also indicate that the statement was not expensive enough to fulfill a condition that only expensive statements be traced.
There are many reasons you may want to examine in detail what activities the database server is performing. These include troubleshooting performance problems, estimating resource usage to plan for future workloads, and debugging application logic.
Troubleshooting performance problems
Detecting slow statements
Detecting when hardware resources are a limiting factor
Debugging application logic
Performing request trace analysis