Microsoft® SQL Server™ logs events to the SQL Server error log and the Microsoft Windows NT® application log (although only certain system events and user-defined events are written to the Windows NT application log).
The SQL Server error log contains more complete information about events in SQL Server. You can use the information in the error log to troubleshoot problems related to SQL Server.
The Windows NT application log provides an overall picture of events that occur on the Windows NT system, as well as events in SQL Server and SQL Server Agent. The Windows NT Event Viewer, used to display the Windows NT application log, allows information that is displayed in this log to be filtered. For example, you can filter event types, such as Information, Warning, Error, Success Audit, and Failure Audit.
Both logs automatically timestamp all recorded events.
You can use both the SQL Server error log and the Windows NT application log to track down the root cause of problems. For example, while monitoring the SQL Server error log, you may detect a certain set of messages for which you do not know the cause. By comparing the dates and times for events between the SQL Server error log and the Windows NT application log, you can narrow the list of probable causes.