SSAS database backup fails with the error 3239837698

Question

When I run XMLA query to backup SSAS database

<Batch xmlns="http://schemas.microsoft.com/analysisservices/2003/engine" Transaction="false" >
  <Backup xmlns="http://schemas.microsoft.com/analysisservices/2003/engine"&gt;
    <Object>
      <DatabaseID>MyDB</DatabaseID>
    </Object>
    <File>D:\SSAS\OLAP\Backup\MyDB.abf</File>
    <AllowOverwrite>true</AllowOverwrite>
  </Backup>
</Batch>

It runs for an hour, creates backup file, and gives me an error:

<return xmlns="urn:schemas-microsoft-com:xml-analysis">
  <results xmlns="http://schemas.microsoft.com/analysisservices/2003/xmla-multipleresults"&gt;
    <root xmlns="urn:schemas-microsoft-com:xml-analysis:empty">
      <Exception xmlns="urn:schemas-microsoft-com:xml-analysis:exception" />
      <Messages xmlns="urn:schemas-microsoft-com:xml-analysis:exception">
        <Error ErrorCode="3239837698" Description="Server: The operation has been cancelled." Source="Microsoft SQL Server 2008 Analysis Services" HelpFile="" />
      </Messages>
    </root>
  </results>
</return>

Log says: `Microsoft.AnalysisServices.Xmla.XmlaException: Server: The operation has been cancelled.

at Microsoft.AnalysisServices.Xmla.XmlaClient.CheckForSoapFault(XmlReader reader, XmlaResult xmlaResult, Boolean throwIfError) at Microsoft.AnalysisServices.Xmla.XmlaClient.CheckForError(XmlReader reader, XmlaResult xmlaResult, Boolean throwIfError) at Microsoft.AnalysisServices.Xmla.XmlaClient.SendMessage(Boolean endReceivalIfException, Boolean readSession, Boolean readNamespaceCompatibility) at Microsoft.AnalysisServices.Xmla.XmlaClient.SendMessageAndReturnResult(String& result, Boolean skipResult) at Microsoft.AnalysisServices.Xmla.XmlaClient.Execute(String command, String properties, String& result, Boolean skipResult, Boolean propertiesXmlIsComplete) at Microsoft.SqlServer.Management.Smo.Olap.SoapClient.ExecuteStatement(String stmt, StatementType stmtType, Boolean withResults, String properties, String parameters, Boolean restrictionListElement, String discoverType, String catalog) at Microsoft.SqlServer.Management.Smo.Olap.SoapClient.SendCommand(String command, Boolean withResults, String properties) at OlapEvent(SCH_STEP* pStep, SUBSYSTEM* pSubSystem, SUBSYSTEMPARAMS* pSubSystemParams, Boolean fQueryFlag)Microsoft.AnalysisServices.Xmla.XmlaException: Server: The operation has been cancelled. `

I am not sure if backup is good.