Recover SQL Data from a Corrupted Transaction Log File

Read time 5 minutes

“Read this blog engagingly to know how to repair corrupted SQL Server transaction log files by executing some workable SQL commands and get back access to your SQL database files once again.”

MS SQL Server, the most commonly used database server, is vulnerable to corruption due to various logical and physical reasons. Let us suppose a situation when you are informed that one of the transaction log files has been corrupt due to some unknown reasons. Because of the transaction log file damage, SQL Server finds it difficult to access the required .mdf file.

It means .mdf file requires recovery, which can be easily done with the backup of MDF file you have. However, in case you do not have a backup of the MDF file, SP_ATTACH_DB_SINGLE_FILE_DB command can be a help for you. The command helps you rebuild the database but only in the following two ways:

Use the SP_ATTACH_DB_SINGLE_FILE_DB command on the MDF file that was previously detached from the server through SP_DETACH_DB command.

Use the SP_ATTACH_DB_SINGLE_FILE_DB command on the MDF file having only one log file.

In case, you do not have any backup of the MDF file and also the SP_ATTACH_DB_SINGLE_FILE_DB command does not help you rebuild the database then execute the following steps (on your own risk) to restore the database:

1. Create a backup of the MDF file.
2. Detach the corrupted database from the server using the SP_DETACH_DB command.
3. Create a new database file having the same name as the damaged database file. The file should have the same path where the log files are stored.
4. Stop SQL Server services.
5. Rename the newly created database file without .mdf extension.
6. Rename the damaged database file as the newly created database file.
7. Start SQL Server services.
8. Open up Query Analyzer and execute SP_CONFIGURE> allow update, 1. You are suggested to use the SP_CONFIGURE system stored procedure with RECONFIGURE WITH OVERRIDE statement if you want the process to take effect immediately without stopping or restarting the Server.
9. Now, update the SYSDATBASES system table by finding DBID settings to 32768 for a corrupted database file.
10. Restart SQL Server services.

Note: The above-mentioned steps are very tricky and could result in data loss. It is recommended that users should perform them in a test environment at their own risk.

The executed steps will repair the damaged MDF file and you will be able to work with it. However, in case these steps do not work, you need to take the help of MDF recovery and repair software. SQL Recovery is well designed and easy-to-use SQL Server data recovery tool. The software recovers database objects like: tables, triggers, rules, functions, deleted records etc. from damaged MDF files created in any SQL Server version. One can recovered data to a live SQL Server or bath file after previewing it.

Let us know the working of the software through these steps:

1. Start the installed software application and add the MDF file for repair using the Browse button. Select any recovery mode as per requirement, SQL database version, and click Recover.
   
2. The SQL database objects will get retrieved. Click on any object to view its complete preview. Then make the selection of data and click Save.
   
3. Choose the saving option – either to live SQL Server or Batch file mode at the system location. Provide the details or saving path and click OK.
   
4. The saving process will start and on completion shows a message. Click OK to finish the process.
   

Thus, recovering data from the corrupt SQL database is an easy affair for Kernel for SQL Database Recovery software. It recovers all database objects quite smoothly.

Conclusion

We have discussed a situation where a transaction log file of the SQL Database gets corrupted. For recovery, manual solutions like the use of backup (if available) and rebuilding of the database to restore the database (if backup not available) are explained. Also, recovery through a third-party tool is explained through screenshots.