Users report that some function has stopped working.

Impact: High

Expected behavior :
The standard threshold setting for this alert should be Critical=0. This alert serves as a notice concerning internal SQL engine-related issues and must be treated with urgency.
There is a wide range of occurrences inside the SQL engine that will stop and report back as a bug – see the summary table in Background

Priority: Critical
Recommended action :
Investigate the cause of the bug. In most cases, running DBCC CHECKDB can resolve (but take note of certain circumstances where some data may be lost.)


Use of the term ‘bug’ should not be confused with an error in the SQL program itself, but usually relates here to some incorrect or inconsistent data.

Suggested action: Run DBCC CHECKDB

  • A read of a file succeeded after failing x time(s) with a specified error. This error condition threatens database integrity and must be corrected.
  • A system assertion check has failed. Check the SQL Server error log for details. Typically, an assertion failure is caused by a software bug or data corruption.
  • An internal error occurred while attempting to convert between compressed and uncompressed storage formats or between variable-length and fixed-length decimal formats.
  • An internal service broker error was detected. Possible database corruption. (see note 3)
  • An internal Service Broker error occurred (error xxxx). This error indicates a serious problem with SQL Server.
  • Attempt to fetch logical page failed.
  • Columnstore index has one or more data values that do not match data values in a dictionary or are inconsistent with data values within the metadata or have one or more missing column segments or one or more missing dictionaries.
  • The connection handshake failed. The certificate used by this endpoint was not found
  • Could not find an entry for index in database ID xxxx. Possible schema corruption.
  • Could not open File Control Block (FCB) for invalid file xxxx in database xxxx. Verify the file location.
  • Internal error. The buffer provided to read column value is too small, or to write a fixed column value is too large.
  • Invalid header value from a page.
  • Metadata inconsistency. The filegroup specified for the table does not exist.
  • No catalog entry was found for partition in the database. The metadata is inconsistent.
  • Possible index corruption detected.
  • Sort operation failed during an index build. The overwriting of the allocation page in the database was prevented by terminating the sort. (It may be necessary to restore the database from the backup.)
  • SQL Server Assertion: File: or File: line or File: line Failed Assertion. The error may be timing-related. If the error persists after rerunning the statement, use DBCC CHECKDB to check the database for structural integrity or restart the server to ensure in-memory data structures are not corrupted.
  • SQL Server detected a logical consistency-based I/O error.
  • The conversation endpoint with conversation handle xxxx is in an inconsistent state. (see note 3)
  • The conversation group exists, but no queue exists or references a missing conversation group. Possible database corruption.
  • The Database/slot for LOB data type node does not exist.
  • The operating system returned an error to SQL Server in file xxxx. This is a severe system-level error condition that threatens database integrity and must be corrected immediately.
  • The service queue structure is inconsistent. Possible database corruption.
  • Unable to find index entries in the index of the table in the database. The indicated index is corrupt or there is a problem with the current update plan. Run DBCC CHECKDB or DBCC CHECKTABLE.
  • Failed to read the message body while marshaling a message. (see note 3)
  • The operating system returned to SQL Server. It failed to create an event in the file.
  • Warning: The log for database xxxx has been rebuilt. Transactional consistency has been lost.


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