Saturday, November 10, 2012

Deadlock Graph XML from Extended Events in SQL Server 2008

We were dealing with some deadlock problems in our database. However, unfortunately we did not have trace flag 1204 and/or trace flag 1222 turned on. Fortunately there is a way to retroactively retrieved deadlock information starting with SQL Server 2008 using Extended Events.

Someone forwarded an article written by Jonathan Kehayias (blog | twitter), an expert in Extended Events, regarding this. The article can be found here. It is a great article. In the article, Jonathan showed us the way to retrieved the deadlock graph from Extended Events.

Jonathan also mentioned in the article that there is a bug in the output of deadlock graph from the Extended Events, in which it is not a valid XML. There is a problem with missing end tag for the <victim-list> node. He then provided a work-around script in which he utilizes the replace function on the deadlock information text from the Extended Events. Then after that we could cast the text as XML.

I went ahead and try that script. When I tried it, I got the following error message:

Msg 9436, Level 16, State 1, Line 1
XML parsing: line 5, character 17, end tag does not match starting

Upon further review, it looks like the script works on deadlocks that have exactly 1 <victimProcess> node. However, if there is empty <victimProcess> node or multiple <victimProcess> nodes, the script would not work. In the case of multiple <victimProcess> nodes, for some reasons, the Extended Events only closed the last <victimProcess> node, but all the other ones are missing the end tag. Thus, I made a small tweak to Jonathan’s script to handle empty <victimProcess> node or multiple <victimProcess> nodes. Here’s the script:


                        REPLACE(XEventData.XEvent.value('(data/value)[1]', 'varchar(max)'),
                        '<victimProcess', '</victimProcess><victimProcess'),
                    '<victim-list>', '<deadlock><victim-list><victimProcess>'),
                '<process-list>', '</victim-list><process-list>'),
            '<victim-list/>', '<deadlock><victim-list>'),
        '<victimProcess>' + CHAR(10) + SPACE(2) + '</victimProcess>', '') AS XML) AS DeadLockGraph
(SELECT CAST(target_data as XML) AS TargetData
FROM sys.dm_xe_session_targets st
JOIN sys.dm_xe_sessions s ON s.address = st.event_session_address
WHERE name = 'system_health') AS Data
CROSS APPLY TargetData.nodes ('//RingBufferTarget/event') AS XEventData (XEvent)
WHERE XEventData.XEvent.value('@name', 'varchar(4000)') = 'xml_deadlock_report'


  1. Just what I needed. Many Thanks

  2. Hi can you please help me I am still getting the error

    1. What version of SQL Server and also service pack do you use?

    2. I am using 10.50.4263 and getting an error
      Msg 9436, Level 16, State 1, Line 1
      XML parsing: line 4, character 15, end tag does not match start tag
      Could you please help?