Extended Events is a general event-handling system for performance monitoring that was introduced in SQL Server 2008. It has a highly scalable and highly configurable architecture that allows users to collect as much or as little information as is necessary to troubleshoot or identify a performance problem.
While there are already a number of diagnostics tools such as DBCC, SQL Trace, SQL Server Profiler, DMVs, and Perfmon, Extended Events offer several major advantages: It is light weight, has a highly scalable and highly configurable architecture, it allows a deeper and more granular level control of tracing, and it has more events that can be captured (for example you can identify page splits and high CPU utilization by ad-hoc queries). For further troubleshooting, you can even use Extended Events to correlate SQL Server captured event data. For more info see Opening the SQL Server 2008 Toolbox – An Introduction to Extended Events.
In SQL Server 2012, the following features were added:
Note that with SQL Server 2012, SQL Trace is deprecated. It will be phased out over the next few released in favor of Extended Events.
SQL Server 2012 “Denali”: Extended Discussion On Usage Scenario for “Extended Events” (Part-1)
SQL Server 2012 Extended Events Update – 1- Introducing the SSMS User Interface
SQL Server 2012 Extended Events Update – 2 – The SSMS UI Part 2
What’s New for Extended Events in SQL Server Codenamed “Denali” CTP3
Introducing the Extended Events User Interface
Introducing the Extended Events Reader
Introducing the Extended Events Object Model
What’s new for Extended Events in SQL Server code-named “Denali” CTP1
From the MVPs: A GUI for Extended Events in SQL Server 2012