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Article ID: 2015757 - Last Review: July 9, 2012 - Revision: 5.0

Symptoms

When an I/O error is detected by SQL Server (Msg 823 or 824), it will retry the operation up to four times before failing the read or write operation. If the operation is successful after one of the retry attempts, the query that required the read or write will not fail but you will see a message in the ERROROG like the following:

2010-03-31 21:06:54.34 spid52      A read of the file 'C:\Program Files\Microsoft SQL Server\MSSQL10.SQL2008\MSSQL\DATA\mydb.mdf' at offset 0x00000000132000 succeeded after failing 2 time(s) with error: incorrect checksum (expected: 0xffd99027; actual: 0x331d106f). Additional messages in the SQL Server error log and system event log may provide more detail. This error condition threatens database integrity and must be corrected. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.

An Information Level message will be written into the Windows Appliction Event Log with EventID = 825. Since the operation was successful after one or more retry attempts, the client application does not see any error or this message.

Cause

The cause of this problem is similar to cause as if the Msg 823 or 824 error ccurred. The message in the ERRORLOG contains the proper context including the original error to troubleshoot the possible cause. Please see the causes of Msg 823 or 824 errors in the following articles for more information:

How to Troubleshoot Msg 823 in SQL Server

How to Troubleshoot Msg 824 in SQL Server

Resolution

Since the server has been able to successfully retry the operation, there is no immediate action for you to take. However, the retry operation indicates an underlying problem that should be investigated. You should use the same techniques for this investigation as if a Msg 823 or 824 error occurred. Use the articles listed in the Cause section as a guide.

One consideration is to use the SQLIOSim tool against the drive reporting this message during the next appropriate window to test I/O integrity.

More Information

Msg 825 is often referred as the read retry warning but technically the retry can be for a read or write operation. The message indicates if the operation was based on a read or write. Furthermore, the message indicates the number of retry attempts required for the operation to be successful.

This concept was introduced in SQL Server 2005 because testing and past experience had shown that in some situations an I/O error can be successful if you retry the operation. SQL Server will retry these operations up to four times (this limit is not configurable) and after this raise the original 823 or 824 error. 

For more information about the products or tools that automatically check for this condition on your instance of SQL Server and on the versions of the SQL Server product, see the following table:  

 

 Rule software

 Rule title

 Rule description

 Product versions against which the rule is evaluated

SQL Server 2008 R2 Best Practice Analyzer(SQL Server 2008 R2 BPA)

I/O requests are successful when retried 

 

 

The SQL Server 2008 R2 Best Practice Analyzer (SQL Server 2008 R2 BPA) provides a rule to detect situations in which SQL Server has reported Event ID 825 to the Windows Application Event log. The SQL Server 2008 R2 BPA supports both SQL Server 2008 and SQL Server 2008 R2. 

If you run the BPA tool and encounter the warning, Engine - I/O requests are successful when retried, you need to review the information that is provided in this article and perform the required diagnostics for the storage system that is hosting the volumes that are involved in the 825 events.  

SQL Server 2008
SQL Server 2008 R2

SQL Server 2012 Best Practice Analyzer (SQL Server 2012 BPA)

I/O requests are successful when retried 

The SQL Server 2012 Best Practice Analyzer (SQL Server 2012 BPA) provides a rule to detect situations in which SQL Server has reported Event ID 825 to the Windows Application Event log.

If you run the BPA tool and encounter the warning, Engine - I/O requests are successful when retried, you need to review the information that is provided in this article and perform the required diagnostics for the storage system that is hosting the volumes that are involved in the 825 events.  

 SQL Server 2012

Note This is a "FAST PUBLISH" article created directly from within the Microsoft support organization. The information contained herein is provided as-is in response to emerging issues. As a result of the speed in making it available, the materials may include typographical errors and may be revised at any time without notice. See Terms of Use (http://go.microsoft.com/fwlink/?LinkId=151500) for other considerations.

APPLIES TO
  • Microsoft SQL Server 2005 Developer Edition
  • Microsoft SQL Server 2005 Enterprise Edition
  • Microsoft SQL Server 2005 Express Edition
  • Microsoft SQL Server 2005 Standard Edition
  • Microsoft SQL Server 2005 Workgroup Edition
  • Microsoft SQL Server 2008 Developer
  • Microsoft SQL Server 2008 Enterprise
  • Microsoft SQL Server 2008 Express
  • Microsoft SQL Server 2008 Express with Advanced Services
  • Microsoft SQL Server 2008 R2 Developer
  • Microsoft SQL Server 2008 R2 Enterprise
  • Microsoft SQL Server 2008 R2 Standard
  • Microsoft SQL Server 2008 R2 Web
  • Microsoft SQL Server 2008 R2 Workgroup
  • Microsoft SQL Server 2012 Developer
  • Microsoft SQL Server 2012 Enterprise
  • Microsoft SQL Server 2012 Express
  • Microsoft SQL Server 2012 Standard
  • Microsoft SQL Server 2012 Web
  • SQL Server 2012 Enterprise Core
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