# SDS - Repairing Data

If the database of a controller is severely out of sync, you can restore the database from a backup. However, the backup database will not include the recent database changes that have been made to other systems in the cluster while the controller was down. After performing the data restore, you can bring the controller's database up to date, by performing a Data Repair operation from another controller in the system.

The Data Repair operation overwrites all the shared data, including the user and device data, on the slave controller with the shared data from the master controller.

1. Perform a data restore of the latest backup to the secondary controller.

2. Go to the Network Elements form ( ) of a controller in the cluster that has up to date data.

3. Synchronize the data from the local, master controller to the slave controller. Before you confirm the synchronization operation:

4. Select the Data Repair option in the Confirm Sync to Element(s) window

5. Click the Advanced button

6. Set the Resilient User-Device Policy to "Synchronize data where <local element> is the PRIMARY and SECONDARY host for resilient devices".

7. Click Apply

8. Click OK

Related Topics

- About_Sharing and Synchronizing Data

- About Synchronizing User and Device Data

- Synchronization Rules

- Synchronizing Data