SQL Server is a powerful database management system used by many organizations to store and retrieve data. However, sometimes it may encounter logical consistency-based issues that need to be addressed. In this article, we will explore what these issues are and how to resolve them.
Table of Contents
Table of Contents
Understanding the Issue
Error Details:
Logical Consistency-Based IO Error in SQL Server Database
Logical consistency-based issues in SQL Server can occur when there is a mismatch or corruption in the data stored within the database. These issues can lead to data integrity problems and affect the overall performance of the system.
Common symptoms of logical consistency-based issues include:
- Data inconsistencies or missing data
- Unexpected errors or crashes
- Slow performance
Resolving the Issue
Method 1 – Check hardware and application connectivity of related server and application
MSSQLSERVER_824 – SQL Server
These logical consistency checks are integrity checks performed by SQL Server to ensure key elements of the data that was involved in the I/O …
Database inconsistency error can be resolved by establishing proper connectivity between the database and related application server where some transactions may be in queue to be sent to database server for commit the transactions.
When SQL Server detects a logical consistency-based issue, it is important to take immediate action to resolve it. Here are the steps to follow:
- Identify the specific issue by analyzing error logs and diagnostic information.
- Take a backup of the affected database to ensure data safety.
- Run the DBCC CHECKDB command to check the logical consistency of the database.
- If any errors are detected, use the DBCC CHECKDB command with the REPAIR option to fix them.
- Verify the consistency of the database after the repair process.
DBCC CHECKDB (ABCD) WITH NO_INFOMSGS, ALL_ERRORMSGS
Executing above command highlights the problem in detail, and SQL database may display the I/O error message as follows:
Msg 8906, Level 16, State 1, Line 1
Table error: Object ID 0, index ID -1, partition ID 0, alloc unit ID 0 (type Unknown), page ID (1:1846) contains an incorrect page ID in its page header. The PageId in the page header = (0:0).
Such error messages help us reach a conclusion that SQL Database logical consistency based I/O error is caused either due to hardware issues or due to corruption in SQL database.
Method 2 – Restore from SQL backup taken recently with tail log backup
The most feasible solution is to use backup for SQL database restoration. Before restoring from backup, check that:
- You have a recent full backup
- Backup is updated, just prior to corruption, and not long ago so as to avoid critical data loss
Corruption is at page level, as page level corruption issue can be resolved with the help of page-level restoration.
Please Note: Page-level restoration is valid when you are dealing with large database and corruption is in only in one-page of SQL database.
Step 1: Use the following command for restoring SQL database from full backup
Backup the transaction log
BACKUP LOG Restore1 TO DISK = 'g:Restore1_LOG1.bak' WITH INIT
GO
Step 2: Perform the restoration change to reflect the changes online.
Backup the tail of the log…
BACKUP LOG Restore2 TO DISK = 'g:Restore1_LOG_TAIL.bak' WITH INIT
GO
Note: There is no need to restore full SQL server database if corruption is confined to a single page. You can restore database from the available backup for that page which is corrupted. Performing the following commands will help in restoring backup for a single page:
Restore all available log backups in the correct order
RESTORE LOG Restore1 FROM DISK = 'g:Restore1_LOG1.bak' WITH NORECOVERY
GO
— Finally restore the tail log backup
RESTORE LOG Restore1 FROM DISK = 'g:Restore1_LOG_TAIL.bak' WITH NORECOVERY
GO
— Finally finish with the restore sequence
RESTORE DATABASE Restore1 WITH RECOVERY
GO
Once the database backup has restored SQL database, run the query DBCC CHECKDB again to check that the select statement succeeds without SQL Database logical consistency-based I/O error. This command also checks that there is no data loss in this table.
Limitations of SQL database backup method:
It is not possible to restore from SQL database backup when the available backup is obsolete.
If Logical consistency based I/O error is spread across the SQL server database, then this method will not be valid.
For those cases where faulty page exists in a non-clustered index, the SQL database can be fixed by dropping and recreating the index of SQL database.
Method 3: Repair corrupt SQL database with REPAIR_ALLOW_DATA_LOSS
REPAIR_ALLOW_DATA_LOSS is the minimum repair level for the diagnosed errors.
Please Note: Before using REPAIR_ALLOW_DATA_LOSS, perform the following:
- Take a backup of SQL server database and save it with another name
- Set SQL database in Single user mode
- Get all Tables record count by using the following commands
DECLARE @T_Name VARCHAR(250)
DECLARE @COUNT INT
DECLARE @SQL VARCHAR(2000)
CREATE TABLE #T_Info(ID INT IDENTITY(1,1),T_Name VARCHAR(200),D_Count INT)
DECLARE TINFO_CUR CURSOR FOR
SELECT TABLE_NAME FROM INFORMATION_SCHEMA.TABLES
WHERE TABLE_TYPE='BASE TABLE'
OPEN TINFO_CUR
FETCH NEXT FROM TINFO_CUR INTO @T_Name
WHILE @@FETCH_STATUS =0
BEGIN
SET @SQL='INSERT INTO #T_Info(T_Name,D_Count) SELECT '''+@T_Name+''',COUNT(*) FROM '+@T_Name+''
EXECUTE (@SQL)
FETCH NEXT FROM TINFO_CUR INTO @T_Name
END
CLOSE TINFO_CUR
DEALLOCATE TINFO_CUR
SELECT * FROM #T_Info ORDER BY T_NAME
The following steps help to fix SQL database and resolve logical consistency based I/O error:
4.Run the command:
DBCC CHECKDB (DB_NAME, REPAIR_ALLOW_DATA_LOSS)
Once SQL database is repaired, repeat the process of ‘Table Record Count’ and compare with old record count.
There must not be any difference between initial and final Table record count.
Limitations:
REPAIR_ALLOW_DATA_LOSS may fix Database logical consistency-based IO error but there is a major issue of data loss, where an organization may experience loss of critical data.
Alternative Solution
If above methods won’t work then, give a try to a SQL Recovery Software. Stellar Repair for MS SQL repairs corrupt MDF and NDF files and restores all the database objects. It supports MS SQL 2019 and all the lower versions.
Conclusion
In this post, we have highlighted the cause of SQL Database logical consistency-based I/O error and the methods to detect this error.
Based upon the error, we have tried to find the correct resolution method. If hardware or system is responsible for the error, it is recommended to resolve the hardware-related issues, and in case DBCC CHECKDB reports consistency error, then try to restore SQL database by using an updated backup.
If the issue is not resolved with hardware correction and backup then try to repair the database with the help of REPAIR_ALLOW_DATA_LOSS. This is the minimum level of repair to resolve all errors from CHECKDB, but this does not mean that it will actually fix the error. Furthermore, it may result in data loss.
SQL repair tool helps in repairing corrupt MS SQL database including corrupt .mdf and .ndf files and recovers all database components – Tables, Triggers, Indexes, Keys, Rules, deleted records and Stored Procedures. It is of great help in times of crisis, as the software provides a definite repair solution and supports all SQL database versions including the recent and older ones.
Preventing Future Issues
While it is important to resolve the current logical consistency-based issue, it is equally crucial to prevent future occurrences. Here are some preventive measures:
- Regularly perform database maintenance tasks such as index rebuilds and statistics updates.
- Monitor the system for any signs of performance degradation or data inconsistencies.
- Implement proper backup and recovery strategies to ensure data safety.
- Stay up-to-date with SQL Server patches and updates.
By following these preventive measures, you can minimize the chances of encountering logical consistency-based issues in the future.