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TN Hist227 Historian Event System High CPU Utilization

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This tech note from InSource details a high CPU utilization issue and fix for the Wonderware Historian Event System.


  • Author: Rich Brooks
  • Published: 9/28/2015
  • Applies to: Historian v11.6 and higher




A high CPU utilization issue was encountered following the migration of a Wonderware Historian from v9.0 to v11.6.  The Historian had four events configured.  The server was running at 100% CPU utilization with the events enabled.  This caused applications on the machine to run slow.


Several SQL Profiler traces were created to troubleshoot the issue.  This identified the execution of stored proc aaSummaryActionInsert against the runtime database as throwing the exception "Conversion failed when converting date and/or time from character string."  This was causing a high CPU usage for the SQL server process. Queries with datetime of type DateTime2 were throwing exceptions against the runtime database.  DateTime2 was not supported in SQL Server 2005


The solution was to modify the Compatibility level setting for the runtime database.  This is changed from 2005 to 2012 in SQL Server Management Studio.  Right click on the Runtime database to open the properties dialog.  The following is a screen capture from SQL Server.



The CPU Utilization will return to normal following this change.