SQL Server administrators are responsible for managing the database and bringing back the server, services, and data in case of a disaster, ransomware attack, system crash, or any other critical failure. This can be easily achieved if they have a proper and well-organized database recovery plan in place. In this article, we will be discussing how to build a SQL Server recovery plan that can help to restore and recover the data with minimum downtime, in case of a disaster or critical system failure. It includes best practices, effective methods to repair and restore corrupt MDF files, and the role of keeping a professional SQL recovery tool handy.
What is SQL Server Database Recovery?
SQL Server database recovery is the process of restoring corrupt database after a critical failure or other disruptive event. It allows complete database recovery even when backups are incomplete or transaction log files are missing. The process covers restoring from backups and using advanced data recovery methods, along with specialized SQL recovery tools.
Types of SQL Server Database Failures that require Data Recovery
It is quite important to understand the common scenarios where your database can become inaccessible. This knowledge helps you to quickly apply the right recovery approach for each specific case. Some of the common scenarios are listed below:
- Missing Transaction Log Files: You might be getting attaching or detaching errors. In this case, the point-in-time recovery is impossible. You have to rely on repair tools.
- Database won’t Start Issue: Your SQL Server instance fails to open the database. This can happen due to corruption in MDF/NDF files.
- Database is in Suspect/Recovery Mode: Your database status is marked as suspect or recovery pending. It usually takes place due to corruption in the SQL database.
- Problem in MDF/NDF Files: Corruption-related issues appear in your SQL error log or DBCC CHECKDB returns errors related to damage in tables, stored procedures, or indexes in primary (MDF) or secondary (NDF) data files.
Tips to Build an Effective SQL Server Recovery Plan
Here are the key components you should consider before building a SQL Server database recovery plan:
Backup Type and Strategy
Backup strategy is an important aspect for disaster recovery. There are different types of backups you can use. Common ones are:
- Full Backups: Full backups are regular comprehensive backups of all the databases. This means that the entire database file is fully backed up and is independent. However, it would require time to finish and huge storage resources.
- Log Backups: In this type of backup, a full backup is taken the first time and then the backups of changes since the previous backup. This is faster and uses less storage space. However, every backup is dependent on all the previous backups till the full backup.
- Differential Backups: This type of backup is similar to incremental backup, but the only difference is that each backup is independent. It only depends on the first full backup. This is slightly slower and uses more space than the incremental backup.
- Partial Backups: This type of backup is used to exclude read-only file groups. It is created to improve flexibility to back up large-sized databases containing multiple read-only file groups.
Recovery Model
You should understand the recovery models when planning a SQL Server recovery plan. This helps you to determine the types of backups you can create, how much data you can recover, and how quickly recovery can occur after a failure. Choosing the incorrect recovery model can disrupt your recovery plan. It impacts the Recovery Time Objective (RTO) and Recovery Point Objective (RPO). For example, with the Full model, you can achieve a low RPO, whereas the Simple model may result in higher RPO.
RTO & RPO
Recovery Time Objective (RTO) is the maximum acceptable downtime defined by an organization after a failure, and Recovery Point Objective (RPO) is the maximum acceptable data loss measured in time.
Continuous Monitoring and Alerts
You should regularly check the SQL server error logs and set performance alerts using the Widows Performance Monitor to get alerts when performance metrics fall below or reaches the threshold value. Also, you can run or schedule the DBCC CHECKDB command to detect and fix issues and errors in the MDF/NDF file. This helps you to easily detect symptoms of corruption or other issues, before they lead to complete database failure.
Recovery Strategy
The objective of recovery strategy is to have a full document on whom to contact when the issue occurs and how the recovery process should be executed. The process must be fully documented. If any issues arise, you can follow the document.
According to the situation, you can follow the recovery technique. If the SQL database is corrupted, then you can recover it from the backup. However, any changes in the database from when backup was last updated till when the server has failed will be lost, resulting in data loss. You can even use the native repair command – DBCC CHECKDB – to repair the database if it is slightly corrupted. You can keep a reliable SQL recovery tool, like Stellar Repair for MS SQL in hand. It can repair MDF/NDF of any size with complete integrity. It is particularly useful when the database is corrupted or not available.
Automation with Log Shipping
You should know about a simple and cost-effective high-availability solution – SQL Server log shipping. This feature of SQL Server allows you to replicate the data in one database from one SQL Server instance to another with the help of log backups. In other words, you can say that the regular log backups are sent from a primary to a secondary server, keeping it ready as a warm standby. The main objective of this feature is to minimize data loss. You need to configure this log shipping in MS SQL manually.
Always On Availability Groups
This is a high-availability setup that helps keep the SQL database running. It has multiple servers and nodes, and contains advanced features, like automatic failover, etc. If any of the servers fails, this high-availability setup helps you keep your database accessible.
Step-by-Step SQL Server Data Recovery Planning Process
Here are the steps to plan the SQL Server data recovery:
- Check and Divide the Critical Databases
First, check all the SQL Server databases and classify according to business criticality. This helps you easily identify the critical components that are required to be restored in case of any disaster. You can use sys.databases, system catalog views, etc.
- Define the RPO and RTO
Now define the Recovery Point Objective (RPO) and Recovery Time Objective (RTO) to set the end goal and timelines according to the standard of your organization.
- Choose the SQL Backup Strategy
Choosing the type of backup for database is crucial for restoring the data in case of a failure event. You can select the suitable backup type and take the backups accordingly. For this, you can use customized backup scripts or use the SQL Server Agent jobs or Maintenance plans.
- Test the Backups
You can also perform a full recovery test of the created backups to ensure that the recovery plan will work when needed. You can use the RESTORE VERIFYONLY or the RESTORE command to test the backup.
- Plan the Strategy for Server and Data Recovery
The disaster recovery plan should include all the tools and utilities that can be used to recover the SQL Server databases.
- Restore Backups
In case of corruption or any other issue, the simplest way is to restore the database from the backup. The time of recovery depends on the type of backup you’re using – full, incremental, or differential.
- Use DBCC CHECKDB Command
If the backup (BAK) file is not available or is corrupted, then you can use the built-in utilities in SQL Server, like the DBCC CHECKDB command, to repair the database. This can help repair the SQL database but it may delete rows or pages, resulting in data loss.
- Use Third-Party SQL Recovery Software
To recover the database without data loss and with minimal downtime, you can take the help of a third-party SQL recovery software, like Stellar Repair for MS SQL. The software repairs corrupt MDF/NDF files and recovers all the data, including stored procedures, with integrity. It allows SQL database recovery without the need of transaction log files or backup files.
Video Guide 🡪 SQL database repair with DBCC and Stellar Recovery Software:
- Document the Disaster Recovery Plan
The next step is to document all the recovery steps, escalation paths, and contact lists. It should include the contact details of the designated person, graphical layout of the plan, vital details of the assets and server configuration, RTO and RPO values, etc.
- Assign Roles
Next, assign the responsibility to DBA according to the resource availability.
- Simulate Failures to Check Recovery
Conduct a test environment to check the disaster recovery plan in case of server crash or corruption.
Conclusion
Recovering databases with minimum downtime after a disaster, requires a clear, well-prepared, and actionable disaster recovery plan. In this article, we have explained how to create an effective plan for SQL Server database recovery. Keeping the right tool handy can help you quickly recover the database in the event of a critical server failure. You can use a SQL recovery tool, like Stellar Repair for MS SQL, to make the recovery process as smooth as possible with minimal impact and no data loss.