High availability permits you to provide minimum downtime for BlackBerry® services if BlackBerry® Enterprise Server components stop responding or if they require maintenance. BlackBerry Enterprise Server high availability consists of a minimum of two BlackBerry Enterprise Server instances and the BlackBerry Configuration Database which is replicated across two database servers. High availability is designed so that no single point of failure exists in the BlackBerry® Enterprise Solution that could break the messaging and application data flow to and from BlackBerry devices.

When you configure the BlackBerry Enterprise Server for high availability, you install a primary BlackBerry Enterprise Server and a standby BlackBerry Enterprise Server on different computers within the same network segment. These BlackBerry Enterprise Server instances create a BlackBerry Enterprise Server pair. Both BlackBerry Enterprise Server instances use the same SRP credentials and BlackBerry Configuration Database. You can configure the failover process to be automatic or manual.

The standby BlackBerry Enterprise Server connects to the primary BlackBerry Enterprise Server and checks periodically that the primary BlackBerry Enterprise Server is healthy. The health of a BlackBerry Enterprise Server is determined by thresholds that you can configure. If the health of the primary BlackBerry Enterprise Server falls below the failover threshold or if the primary BlackBerry Enterprise Server stops responding, the standby BlackBerry Enterprise Server tries to promote itself. If the messaging server and the BlackBerry Configuration Database remain available during the failover process, the message delays that users might experience are similar to the delays that users experience when you start a BlackBerry Enterprise Server instance.

• BlackBerry Enterprise Server high availability in a small-scale environment
  
• How the BlackBerry Enterprise Server calculates health scores
  
• Conditions for failover to a standby BlackBerry Enterprise Server
  
• How a primary BlackBerry Enterprise Server demotes itself
  
• Scenario: What happens after a primary BlackBerry Enterprise Server stops responding
  
• Scenario: What happens after the health score of a primary BlackBerry Enterprise Server falls below the failover threshold
  
• BlackBerry Configuration Database high availability
  
• High availability in a distributed environment