Restore Essentials

This section describes the essentials of how to restore a database from a backup in Exasol.

• The database has to be shut down prior to restoring from a backup.
• When the restore has completed, the database will be in the state it was when the backup was started. Any changes applied to the database after the backup start time are lost. Exasol does not support Point-In-Time recovery. A database state from the past can only be reached based on the start times of the available backups.
• The data distribution inside of an Exasol database depends on the number of cluster nodes. Therefore, a backup can only be restored to a cluster with the same number of nodes as the cluster where the backup was taken before.

Restore Types

You can restore a database from a database backup in the following ways:

Blocking Restore

This is the fastest way to restore a database. However, the database cannot be used during the restore process, and connections to the database are prevented until the restore is finished.

Blocking restore is supported from a local archive volume and from a remote archive volume.

When using the ConfD job db_restore, the value for restore_type is blocking.

Non-Blocking Restore

A non-blocking restore allows connections to the database while the restore is ongoing in the background. If sessions request blocks that have not yet been restored, these blocks are restored with priority.

Non-blocking restore is supported from a local archive volume.

When using the ConfD job db_restore, the value for restore_type is nonblocking.

Virtual Access Restore

A virtual access restore is limited to blocks requested by connected sessions. The database is opened in a special state: changes are allowed, but these changes are not persisted on data volumes.

Virtual access restore is supported from a local archive volume.

Virtual restored databases do not count toward the license limit.

When using the ConfD job db_restore, the value for restore_type is virtual access.