It is a set of techniques using which we can monitor and analyze the performance of an application.
It is implemented by using Tracing,debugging,performance counters and Event logs.
Tracing: information about run time code execution.
In ASP.NET , write Trace="true" in Page Directive.
Then write Trace.Warn("categoryname","messagename");
in the .aspx.cs file event handler(Page_Load).
Debugging: For troubleshooting and detecting logical errors in code.
We can use .NET Framework debugging tools like Cordbg.exe for that.
Performance Counters : can be very useful in analyzing the processing
of the program and vital statistics like Memory consumed.
Event Logs: used for writing Error messages in the Windows Event Log.