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MSSQLSERVER_833

Product Name

SQL Server

Event ID

833

Event Source

MSSQLSERVER

Component

SQLEngine

Symbolic Name

BUF_LONG_IO

Message Text

SQL Server has encountered %d occurrence(s) of I/O requests taking longer than %d seconds to complete on file [%ls] in database [%ls] (%d).  The OS file handle is 0x%p.  The offset of the latest long I/O is: %#016I64x.

This message indicates that SQL Server has issued a read or write request from disk, and that the request has taken longer than 15 seconds to return. This error is reported by SQL Server and indicates a problem with the IO subsystem.

Possible Causes

This problem can be caused system performance issues, hardware errors, firmware errors, device driver problems, or filter driver intervention in the IO process.

Troubleshoot this error by examining the system event log for hardware-related error messages. Also, examine hardware-specific logs if they are available.

Use Performance Monitor to examine the following counters:

  • Average Disk Sec/Transfer

  • Average Disk Queue Length

  • Current Disk Queue Length

For example, the Average Disk Sec/Transfer time on a computer that is running SQL Server is typically less than 15 milliseconds. If the Average Disk Sec/Transfer value increases, this indicates that the I/O subsystem is not optimally keeping up with the I/O demand.

Note Note

Disk access can be slowed by an antivirus program. To increase access speed, exclude the SQL Server data files that are specified in the error message from active virus scans.

For more information about I/O errors, see Microsoft SQL Server I/O Basics, Chapter 2 and the Knowledge Base article at http://support.microsoft.com/kb/897284/en-us.

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