Using XEvents in SSAS 2012

One of the few new features in SSAS 2012 Multidimensional is the ability to use Extended Events (XEvents) for monitoring purposes. I was, naturally, curious about how to use them but quickly found that the documentation in Books Online was completely useless – the code example given just doesn’t work. This started a number of discussions with people like Akshai Mirchandani, Nick Medveditskov, Rob Kerr, Greg Galloway, Francesco De Chirico who all helped me get to the point where I had something working, and I’m very grateful to them. This is a short summary of what I’ve learned so far; hopefully some working XMLA samples will be useful to anyone else who is researching this subject.

First of all, here’s a working XMLA command that creates an XEvent trace:

<Create xmlns=http://schemas.microsoft.com/analysisservices/2003/engine 
xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance 
xmlns:ddl2=http://schemas.microsoft.com/analysisservices/2003/engine/2 
xmlns:ddl2_2=http://schemas.microsoft.com/analysisservices/2003/engine/2/2 
xmlns:ddl100_100=http://schemas.microsoft.com/analysisservices/2008/engine/100/100 
xmlns:ddl200_200=http://schemas.microsoft.com/analysisservices/2010/engine/200/200 
xmlns:ddl300_300="http://schemas.microsoft.com/analysisservices/2011/engine/300/300">
    <ObjectDefinition>
        <Trace>
            <ID>XEvent Demo Trace</ID>
            <Name>XEvent Demo Trace</Name>
            <ddl300_300:XEvent>
                <event_session name="xeas" dispatchLatency="1" maxEventSize="4" maxMemory="4" 
                 memoryPartitionMode="none" eventRetentionMode="allowSingleEventLoss" 
                 trackCausality="true">
                    <event package="AS" name="DiscoverBegin" />
                    <event package="AS" name="DiscoverEnd" />
                    <event package="AS" name="QueryBegin" />
                    <event package="AS" name="QueryEnd" />
                    <event package="AS" name="CommandBegin" />
                    <event package="AS" name="CommandEnd" />
                    <event package="AS" name="LockAcquired">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <event package="AS" name="LockReleased">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <event package="AS" name="LockWaiting">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <target package="Package0" name="event_file">
                        <parameter name="filename" value="c:\demo.xel" />
                    </target>
                </event_session>
            </ddl300_300:XEvent>
        </Trace>
    </ObjectDefinition>
</Create>

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The important parts are the list of events, which are the same as the events that can be seen in Profiler (for a full list see here), and the target node which specifies the .xel file to output to.

Once this has been executed in SQL Server Management Studio, you can verify that the trace is running by using the following DMV:

select * from

$system.discover_traces

Here’s what the output is on my machine:

There are three traces shown running here on my SSAS instance and the last in the list is the XEvent trace I’ve just created.

Having run a few queries to make sure there is something in the .xel file, the trace can be stopped by executing the following XMLA:

<Delete xmlns="http://schemas.microsoft.com/analysisservices/2003/engine">
    <Object>
        <TraceID>XEvent Demo Trace</TraceID>
    </Object>
</Delete>

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You can now open the .xel file specified in the original trace definition in SQL Server Management Studio, browse through it, sort, group events and so on:

Instead of outputting to a .xel file, it’s also possible to output to a .etl file by changing the target. Here’s an XMLA command that does this:

<Create xmlns=http://schemas.microsoft.com/analysisservices/2003/engine 
xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance 
xmlns:ddl2=http://schemas.microsoft.com/analysisservices/2003/engine/2 
xmlns:ddl2_2=http://schemas.microsoft.com/analysisservices/2003/engine/2/2 
xmlns:ddl100_100=http://schemas.microsoft.com/analysisservices/2008/engine/100/100 
xmlns:ddl200_200=http://schemas.microsoft.com/analysisservices/2010/engine/200/200 
xmlns:ddl300_300="http://schemas.microsoft.com/analysisservices/2011/engine/300/300">
    <ObjectDefinition>
        <Trace>
            <ID>XEvent Demo Trace</ID>
            <Name>XEvent Demo Trace</Name>
            <ddl300_300:XEvent>
                <event_session name="xeas" dispatchLatency="1" maxEventSize="4" maxMemory="4" 
                memoryPartitionMode="none" eventRetentionMode="allowSingleEventLoss" 
                trackCausality="true">
                    <event package="AS" name="DiscoverBegin" />
                    <event package="AS" name="DiscoverEnd" />
                    <event package="AS" name="QueryBegin" />
                    <event package="AS" name="QueryEnd" />
                    <event package="AS" name="CommandBegin" />
                    <event package="AS" name="CommandEnd" />
                    <event package="AS" name="LockAcquired">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <event package="AS" name="LockReleased">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <event package="AS" name="LockWaiting">
                        <action package="Package0" name="callstack"></action>
                    </event>
                    <target package="Package0" name="etw_classic_sync_target">
                        <parameter name="default_etw_session_logfile_path" value="c:\demo.etl" />
                    </target>
                </event_session>
            </ddl300_300:XEvent>
        </Trace>
    </ObjectDefinition>
</Create>

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This gives you something that can opened in Windows Performance Analyzer: