There are 2 levels of high availability, application level and database level.
On the application level, a customer can deploy multiple instances of the DualShield servers to achieve high availability. After adding and configuring multiple instances of the DualShield servers in your network, you can configure failover and balance the load across all instances of the DualShield servers. To do so, you must place a load-balancer in front of the cluster of multiple instances of the DualShield servers.
On the database level, high availability is achieved by the SQL server used by the DualShield server. DualShield supports MySQL, Microsoft SQL and Oracle SQL. All of those SQL servers support high availability.
Generally speaking, there are 2 types of SQL high availability clusters, namely Mirroring Cluster and Replication Cluster.