This document discusses Extended Events in SQL Server. It provides an overview of Extended Events, their architecture and components. It also discusses how Extended Events can be used to troubleshoot issues like excessive CPU usage. Finally, it covers different ways of working with Extended Events through T-SQL, SQL Server Management Studio and the SQL Server 2012 interface.
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Extended events
1. Extended Events
Not so tricky as you might think
Jonathan Allen
@fatherjack
sqlsouthwest.co.uk
2. Who on Earth is Jonathan Allen?
Local Government 13 years – accountancy / tax collection.
Systems engineer and DBA since 1999
SQL Server 6.5, 7, 2000, 2005 and 2008+R2, 2012
Blog, Twitter, SQL South West user group
3. What's coming up
• XE - architecture and components.
• What can Extended Events show us?
• Getting started.
• System Health Extended Events session.
• Working with XE.
– T-SQL.
– Extended Events manager SSMS Add-in.
– SQL Server 2012 interface.
14. What can Extended Events show us?
From BOL:
Troubleshooting excessive CPU usage
You are investigating excessive CPU usage on your production system. You use various Dynamic
Management Views (DMVs) to determine if the CPU usage can be attributed to queries that were
run on the system. This examination indicates that most of the queries are ad-hoc user queries.
The information obtained from the DMVs is not enough to diagnose the problem.
You create an Extended Events session that:
• Enables events for statement completion with predicates that specify CPU threshold.
• Has an action to only collect the query plan when the event fires.
• Writes any data that is collected to a file. This file is on a drive that does not contain any log or
database files.
After starting the Extended Events session you examine the output and are able to determine that
the cause of the CPU problem is a data type conversion between two commonly joined tables.
(http://msdn.microsoft.com/en-us/library/bb630354(SQL.100).aspx)
15. Working with Extended Events
Options
• SQL 2008, 2008 R2
– TSQL
– Extended Events Session Explorer
• SQL 2012
– TSQL
– SSMS (not effective on prev. versions)
18. XE Best Practice / Recommendations
Consider
• Target – Sync or Async
• Storage – type, size
• Retention – No_Event_Loss or
Allow_Single_Event_Loss/Allow_multiple_Event_Loss
• Use SSMS 2012 to build session, script it, apply to 2008
19. Reference
• Jonathan Kehayias
– http://twitter.com/#!/sqlpoolboy / http://www.sqlskills.com
– http://extendedeventmanager.codeplex.com/
– http://sqlblog.com/blogs/jonathan_kehayias/archive/2010/12.aspx
• MVP Deep Dives 1
– Chapter 49 by Christian Lefter – via Amazon among other book sellers
• SQL Server 2008 Internals and Troubleshooting
– (Bolton, Langford, Ozar, Rowland-jones, Wort) via Amazon among other book sellers
• Adam Machanic – blog (code generator/tips+advice)
– http://sqlblog.com/blogs/adam_machanic/archive/tags/extended+events/default.aspx
20. Reference
• SQL 2012 SSRS performance reports
– http://www.microsoft.com/download/en/details.aspx?id=29063
• Books Online
– 2008 - http://msdn.microsoft.com/en-us/library/bb677357(v=SQL.100).aspx
– 2012 - http://msdn.microsoft.com/en-us/library/ms130214(v=sql.110).aspx
• MSDN Convert Trace to XE article
– http://msdn.microsoft.com/en-us/library/ff878114(v=sql.110).aspx
• MSDN Blog – Grant Fritchey
– http://blogs.msdn.com/b/microsoft_press/archive/2012/03/21/from-the-mvps-a-gui-for-extended-
events-in-sql-server-2012.aspx
How many people are moving to SQL 2012 right away?Count using versions – 2000 ?!, 2005, 2008+R2Does any have experience of writing code – C, VB, etc ?Taking you from what Extended Events are and how they fit in with SQL Server, through using the default session to keep an eye on your servers to creating your own Event Sessions to check for important events and potential problems.
How many people are moving to SQL 2012 right away?Count using versions – 2000 ?!, 2005, 2008+R2Does any have experience of writing code – C, VB, etc ?Taking you from what Extended Events are and how they fit in with SQL Server, through using the default session to keep an eye on your servers to creating your own Event Sessions to check for important events and potential problems.
Lightweight event handling platform, specifically designed to be used to trouble shoot performance issue and monitoring system performancePreviously to SQL 2005 SQL Trace has been used but always had the overhead, or at least the concern of it, and the risk of masking the issue or making it worse. You could use “server side traces” rather than the SQL Profiler tool but it was still a measurable drag on the system it was monitoring.
Packages are the containers, or groups, for events. There are four packages registered to the Extended Events engine, although one of those is essentially inaccessible to the DBA, and they contain between them all Extended Events objects.
Events – these are known points in code that are of interest. They are categorised in such a way as to align with ETW categories. Channels (interested party – Admin, analytic, Debug + Operational) and keywordsActions – these extend the event in various ways, collecting extra data, aggregating data, getting a stack dump storing state information and even adding a debug breakpoint. Be careful using that one. SQL Server stops!Types –The type is the format of the event data, int32, unicode_stringetcMaps – the way to decode the internal values to an english descriptionTargets – where the collected information is sent. Some targets are only usable with sync or async collection, some can work with both.Predicates – effectively the where clause of the event data collection. Supporting short circuiting so as to allow for max efficiency in what data is collected. Evaluated to a boolean true/false
A session is a collection of events (including the specified actions and predicates), the targets that have been configured and the details of the buffers where the collected data will be sent/stored
Some buffers EG a Deadlock session may have the [sqlserver].[xml_deadlock_reported] event with the [Package0].[ring_buffer] set to a 2MB memory limitA StmtCompleted session might catch the [sqlserver].[sql_statement_completed] event and use the [Package0].[ring_buffer] with a Max_memory setting of 8MB
The pool of threads which make up the mechanism throughwhich the session output it gathered and passed into the chosen targets.Details from sys.dm_os_dispatcher_pools
The individual thread.
Several common examples in Books Online but XE can do so much more.Detecting excessive CPU, Deadlocks, Page Splits, Plan Cache use / non-use the list goes on.
Introduced in 2005 so if you manage 2000 then you still need to use Profiler/TraceNo GUI until Jonathan Kehayias created the XE Session Explorer SSMS addin – available via codeplex
