Know the Finest Way to Run DBCC CHECKDB Repair_Allow_Data_Loss

User Query:

“I was running SQL Server but suddenly I got this error message “DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS”. I was unable to understand what to do next. In fact, I searched for many solutions but, unable to figure out what is the main problem with the SQL database. Can anyone suggest me a dependable approach to fix this problem? Thanks in advance!”

The DBCC CHECKDB command is executed on SQL Server to check the logical and physical integrity of all objects in the database. These components may include pages, values, index relationships, tables, and triggers. This procedure involves many structural integrity checks. In case, any check fails while running the DBCC command, the application may encounter an error message. Due to various problems, there is a need to run SQL DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS command on the database components. Therefore, in the upcoming section, we are going to discuss an instant and reliable solution to fix this issue. Before proceeding, we will show the screenshot of SQL syntax:

Also Read: How to Deal With DBCC CHECKDB Job failed in SQL Server issue

Table of Content

• Understanding Causes of Database Corruption Issues
• Resolve DBCC CHECKDB Repair_Allow_Data_Loss Manually
• How To Execute REPAIR_ALLOW_DATA_LOSS Manually
  • Steps to Execute the Command
  • Why DBCC Suggests This Repair Mode?
• Automated Software to fix Database Corruption Issues
• Conclusion
• FAQs

Understanding Common Causes of Database Corruption

Here are some of the reasons that might lead to a possible database corruption in SQL Server and can further result in damaging the files and making them inaccessible to be use. Let’s take a look at these causes and understand how DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS helps with resolving such issues. 

• Power Outage or abrupt shutdown of the SQL Server database
• Due to hardware failures and file system issues
• Malware attacks on the server or a virus
• Disk space insufficiency 

These are all the reasons that can lead to a possible database corruption and further lead to permanent data loss within the database. We will now take a look at how REPAIR_ALLOW_DATA_LOSS works to repair this issue and further fix the database corruption.

Method to Resolve DBCC CHECKDB Repair_Allow_Data_Loss

Go through the following technique by which users can fix SQL server with corruption issues. Let us have a look:

When setting up a database in an emergency mode using the ALTER DATABASE statement, the DBCC CHECKDB command will perform specific types of special fixtures on the database if the REPAIR_ALLOW_DATA_LOSS option is specified. These allow unrecoverable databases to bring them back online at the consistent state. This must be used as a last resort and only when you are unable to restore the database from backup. When the whole database is set to emergency mode, the database is marked as READ_ONLY, logging is disabled, and limited access to members of the sysadmin fixed server role.

How to Safely Execute the DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS Command?

Here are the prerequisites and the measures that will allow the users to safely execute the command and repair the database corruption and damage in the database. 

Prerequisites for Safer Execution of the Command

Before executing the command, the users need to keep track of the following things:

• Only execute the command when all the other methods have failed, as the command is quite risky to implement. 
• It is crucial for the users to set the database in EMERGENCY mode before beginning the command. 
• Furthermore, it is necessary to take a copy of the corrupted database for backup purposes. 

Safely Execute the DBCC CHECKDB Command in SQL Server Database

For a safer Execution of the command, the users to follow the steps in the right manner. We will now take a look at the steps to be followed.

1. It is important for the users to set the database in emergency mode first.
   

   ALTER DATABASE [DBName] SET EMERGENCY;

2. Now, to put the database into single-user mode, use the given command:
   

   ALTER DATABASE [DBName] SET SINGLE_USER;

3. Next, run the command to repair the database corruption.
   

   DBCC CHECKDB ([DBName], REPAIR_ALLOW_DATA_LOSS);

4. After the command is successfully executed, set the database back to multi-user mode.
   

   ALTER DATABASE [DBName] SET MULTI_USER;

This is the accurate format to repair the corruption in the database and access it in a hassle-free way for day-to-day tasks.
When the SQL database stuck in emergency mode and DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS steps are executed, the following actions are to be taken:

• DBCC CHECKDB uses all pages that have been marked as inaccessible because of checksum or I/O errors if such errors cannot occur. It will also increase the chances of data recovery from a database.
• DBCC CHECKDB attempts to restore the SQL database by using log-based recovery technique.
• Due to transaction log corruption, the database restoration is not possible and transaction logs are being rebuilt. Rebuilding the transaction log files may result in a lack or issues in transaction consistency.
• If DBCC CHECKDB succeeds, the database comes in a consistent state and its status is set to online. Although, the database contains more than one transaction inconsistencies. It is highly recommended you can run DBCC CHECKCONSTRAINTS to recognize every business flaws and keep the database backup instantly. In case, if DBCC CHECKDB command fails, the database cannot be retrieved.

Also Read: Learn How to Execute DBCC CHECKDB Repair_Rebuild Example Command Easily

Why Does DBCC Suggest REPAIR_ALLOW_DATA_LOSS?

As we all are now aware, what the DBCC command is and why it is used, let’s now take a look at the reasons why this command is suggested when corruption or damage occurs in the database. When the database encounters severe corruption, it is not easy to fix it using the REPAIR_REBUILD or REPAIR_FAST modes; hence, the tool suggests using the DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS option. Here are a few scenarios where it becomes crucial for the users to execute this command and further resolve the issue with it. 

• This repair mode is suggested when the database files MDF and NDF are damaged and the repair is too complex for the users.
• When the internal metadata of the database structures is damaged or corrupted, this can also lead to bigger issues and require this mode of repair to fix the error. 
• In case of corruption in the database indexes or rows that are too complex to be repaired, this mode is helpful. 

These are a few scenarios that require the users to choose the REPAIR_ALLOW_DATA_LOSS option, irrespective of the possible risks this issue comes with. However, there are still a few situations where users must not use the  DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS command, such as:

• In case the user has a valid backup, it is safer to recover the database using the backup file only.
• For any minor corruption that can be repaired using other methods, it is better not to use the REPAIR_ALLOW_DATA_LOSS for database recovery. 
• When the database is in a production environment, it is better to avoid the repair process during that time. 
• If you haven’t checked the scope of the corruption, it is suggested not to jump into a repair method and first analyze the corruption. 

Is there any Smart Solution to Fix SQL Database Corruption?

If users are unable to implement any of the stated methods using DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS, they can opt for an automated solution SQL Recovery Software. This utility can help users avoid DBCC repair_allow_data_loss cmd and go for a better alternative.

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With the help of this tool, users can get rid of corruption issues in both MDF and NDF files. The users can also restore deleted SQL Database tables without any data loss. Additionally, it is capable enough to bring back all tables, triggers, stored procedures, functions, views, rules, and corresponding Primary Key. This software is compatible with all Windows versions including Win 10. Furthermore, learn how to remove corruption from SQL Server here:

1. Download and Install the software on your PC.
2. From the menu bar, click the Open button to browse and open the specific MDF file from its location.
3. Choose Quick Scan for normal database corruption. This option will be used to scan MDF files.
4. Check Auto-detect option, if you automatically want to detect SQL Server version of MDF file.
5. After that, you can preview all the components of MDF or NDF file.
6. Finally, you can successfully export the .mdf file with the only Schema or with Schema & Data.

Time to Conclude

Microsoft SQL is one of the major platforms used to manage and keep data safe. However, while executing DBCC, the application will report an error message “DBCC CHECKDB REPAIR_ALLOW_DATA_LOSS”. Thus, in this blog, we have discussed two manual methods through which one can resolve this issue.

If the manual technique fails to fix corrupt SQL database files, then you can take help of modern tool. It is the best solution which helps to rectify damaged, lost, or deleted SQL database successfully. It is capable enough to auto-fetch SQL server name while moving to the SQL database.

Frequently Asked Questions