SQL Server error 833

Error ID: SQL Server error 833

Error Message:

“SQL Server has encountered %d occurrence(s) of I/O requests taking longer than %d seconds to complete on file [%ls] in database.”


This occurs when a read or write request from a disk takes longer than a set period of time to complete, normally 15 seconds. Disk seek time for most standard disks occurs in 10 milliseconds or less. Therefore, 15 seconds is a very long time for the system I/O path to return to SQL Server.  This often indicates a performance issue with I/O access to storage, however it can also result from too much contention for storage access from within SQL Server.


First review the SQL Server WAIT stats to determine where the problem is occurring.  If it is external to SQL Server, then start to look at the external Event Viewer logs. The system event logs should be reviewed to see if they show any hardware related error messages.  In addition, hardware specific error logs should be reviewed to see if they provide any information.  Performance Monitor can be used to monitor the following counters which will give an indication of how the underlying subsystem is performing.


  • Average Disk Sec/Transfer
  • Average Disk Queue Length
  • Current Disk Queue Length


Whatever errors are presented at the hardware / subsystem level should be investigated by your infrastructure / server / network support teams.

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