Five SQL Server Error Log Messages You Should Care About

Introduction

SQL Server error logs are a treasure trove of information, containing important details about the health and performance of your database server. These logs are essential for troubleshooting issues, identifying potential problems before they escalate, and ensuring the overall stability of your SQL Server environment. By regularly monitoring and understanding the contents of these logs, database administrators (DBAs) can proactively manage their servers and avoid catastrophic failures. In this blog post, we will highlight five specific error log messages that should immediately catch your attention, explain what they mean, and outline the steps you should take when you encounter them.

Five SQL Server Error Messages to Watch Out For

1. Error 823: I/O Errors

Example Message:

Msg 823, Level 24, State 2, Line 1
The operating system returned error 21(The device is not ready.) to SQL Server during a read at offset 0x00000000000000 in file 'C:\SQLData\mydatabase.mdf'. Additional messages in the SQL Server error log and system event log may provide more detail. This is a severe system-level error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.

Error 823 indicates an I/O error, suggesting that SQL Server is having trouble reading or writing data to disk. This is a serious error because it often points to underlying hardware issues, such as failing disks or problems with the storage subsystem. When you encounter this error, your first step should be to check the system event logs for more detailed information about the error. Running a full database consistency check (DBCC CHECKDB) is also necessary to assess and repair any potential corruption. If the problem persists, you may need to involve your hardware team to investigate and resolve any physical storage issues.

For further reading, visit Microsoft’s documentation on Error 823.

2. Error 824: Logical Consistency Errors

Example Message:

Msg 824, Level 24, State 2, Line 1
SQL Server detected a logical consistency-based I/O error: incorrect checksum (expected: 0x3f1f1e1e; actual: 0x3f1f1e00). It occurred during a read of page (1:123) in database ID 10 at offset 0x000000001E0 in file 'C:\SQLData\mydatabase.mdf'. Additional messages in the SQL Server error log and system event log may provide more detail. This is a severe error condition that threatens database integrity and must be corrected immediately. Complete a full database consistency check (DBCC CHECKDB). This error can be caused by many factors; for more information, see SQL Server Books Online.

Error 824 signifies a logical consistency error during a read or write operation. This could be due to corrupt pages within the database file, often caused by disk issues or a sudden power loss. Similar to Error 823, your immediate response should be to run DBCC CHECKDB to check the integrity of your database and attempt repairs. Additionally, reviewing the error log and system event log can help you pinpoint the cause of the issue. If these errors are frequent, it may be necessary to restore from a recent backup to ensure data integrity.

For further reading, visit Microsoft’s documentation on Error 824.

3. Error 9001: Log File Errors

Example Message:

Msg 9001, Level 21, State 1, Line 1
The log for database 'mydatabase' is not available. Check the event log for related error messages. Resolve any errors and restart the database.

Error 9001 indicates that the transaction log for a database is not accessible, which can halt database operations. This could be due to a full disk, file corruption, or other I/O issues. When this error appears, start by checking the SQL Server error log and the Windows event log for additional details. Ensure there is enough disk space and that there are no disk failures. Running a consistency check on the transaction log file and considering a log backup or truncation might also be necessary to resolve this issue.

For further reading, visit Microsoft’s documentation on Error 9001.

4. Error 1105: Insufficient Disk Space

Example Message:

Msg 1105, Level 17, State 2, Line 1
Could not allocate space for object 'dbo.MyTable' in database 'mydatabase' because the 'PRIMARY' filegroup is full. Create disk space by deleting unneeded files, dropping objects in the filegroup, adding additional files to the filegroup, or setting autogrowth on for existing files in the filegroup.

Error 1105 occurs when SQL Server cannot allocate space for database objects because the filegroup is full. This is usually due to insufficient disk space or improper autogrowth settings. To resolve this, you can free up disk space, add new files to the filegroup, or adjust the autogrowth settings to allow SQL Server to manage the file sizes automatically. Regular monitoring of disk usage and file growth settings can prevent this error from occurring.

For further reading, visit Microsoft’s documentation on Error 1105.

5. Error 17883: Scheduler Errors

Example Message:

Msg 17883, Level 20, State 1, Line 0
The Scheduler 0 appears to be hung. SPID 55, ECID 0, UMS Context 0x037F8020.

Error 17883 indicates a problem with the SQL Server scheduler, suggesting that a thread is stuck and not progressing. This can be due to high CPU usage, blocking, or other resource contention issues. When this error appears, you should examine the SQL Server error logs, system performance counters, and possibly the Windows event logs for clues. Investigate any long-running queries or processes that might be causing the scheduler to hang. If necessary, restart SQL Server to clear the hung scheduler.

For further reading, visit Microsoft’s documentation on Error 17883.

Importance of Monitoring Other Logs

While SQL Server error logs are essential, it is equally important to monitor Windows, application, and cluster logs. These logs provide additional context and can help identify underlying issues that affect SQL Server performance and stability. For instance, Windows logs can reveal hardware failures, application logs can indicate issues with third-party software, and cluster logs can highlight problems in a high-availability setup. By keeping an eye on these logs, DBAs can gain a comprehensive view of their environment and address potential issues before they impact SQL Server.

Conclusion

Monitoring SQL Server error logs is a vital task for any DBA. By understanding and responding to important error messages, you can maintain the health and performance of your databases. Errors such as 823, 824, 9001, 1105, and 17883 require immediate attention and a structured approach to troubleshooting and resolution. Additionally, don’t overlook the importance of other logs like Windows, application, and cluster logs, as they provide essential insights into your server’s overall health. Regular log monitoring and proactive management will help ensure your SQL Server environment runs smoothly and efficiently.