Database: Extended Events
Extended Events is a powerful and lightweight event-handling system that is built into the Microsoft SQL Server database engine. It provides a more efficient and flexible mechanism for monitoring and troubleshooting SQL Server performance issues compared to the older SQL Trace and Profiler technologies.
Getting Started with Extended Events
To start using Extended Events, you need to create an event session. Here is an example of creating a simple event session to capture deadlock events:
```sql CREATE EVENT SESSION DeadlockEvents ON SERVER ADD EVENT sqlserver.xml_deadlock_report ADD TARGET package0.asynchronous_file_target (SET filename='C:\ExtendedEvents\Deadlocks.xel') ```This code snippet creates an event session called DeadlockEvents that captures deadlock events and writes them to a file named Deadlocks.xel in the C:\ExtendedEvents directory.
Analyzing Extended Events Data
Once you have captured some events in your event session, you can analyze the data using the sys.fn_xe_file_target_read_file function. Here is an example of how to read the data from the Deadlocks.xel file:
```sql SELECT * FROM sys.fn_xe_file_target_read_file('C:\ExtendedEvents\Deadlocks.xel', NULL, NULL, NULL) ```This query reads the data from the Deadlocks.xel file and returns it in a tabular format for analysis.
Common Use Cases for Extended Events
Extended Events can be used for a variety of monitoring and troubleshooting tasks, including:
- Performance tuning
- Deadlock analysis
- Query execution analysis
- Security auditing
Importance of Extended Events in Interviews
Extended Events is a popular topic in database interviews, especially for SQL Server DBAs and developers. Employers often ask candidates about their experience with Extended Events and how they have used it to solve performance or troubleshooting issues.
Conclusion
Extended Events is a valuable tool for monitoring and troubleshooting SQL Server performance issues. By creating event sessions, capturing events, and analyzing the data, you can gain valuable insights into your database's behavior and optimize its performance.
