To configure BlackBerry® Collaboration Service high availability so that instant messaging is not impacted if a BlackBerry Collaboration Service stops responding, you can configure a BlackBerry Collaboration Service pool of two or more BlackBerry Collaboration Service instances. The BlackBerry Enterprise Server and BlackBerry Collaboration Service instances can connect to each other.

After you configure a pool, the BlackBerry® Enterprise Server assigns one of the connections to the BlackBerry Collaboration Service instances as the active connection, and the other connections as standby connections. Multiple BlackBerry Enterprise Server instances can use a single BlackBerry Collaboration Service pool and assign an active connection to different BlackBerry Collaboration Service instances. You can configure manual or automatic failover.

Each BlackBerry Collaboration Service instance writes its health information to the BlackBerry Dispatcher. If the BlackBerry Collaboration Service cannot connect to the primary BlackBerry Dispatcher instance, the BlackBerry Dispatcher can promote another BlackBerry Collaboration Service instance by changing the standby connection to an active connection. When the BlackBerry Collaboration Service with the active connection to the BlackBerry Enterprise Server stops responding, all open instant messaging sessions are lost.

If multiple BlackBerry Collaboration Service instances with standby connections to the BlackBerry Enterprise Server exist, the BlackBerry Dispatcher uses the health score of the BlackBerry Collaboration Service instances to determine which BlackBerry Collaboration Service it assigns the active connection to. The BlackBerry Enterprise Server assigns the active connection to the BlackBerry Collaboration Service instance with the highest score.

• BlackBerry Collaboration Service high availability in a small-scale environment
  
• BlackBerry Collaboration Service high availability in a large-scale environment
  
• Best practice: Planning for BlackBerry Collaboration Service high availability
  
• Scenario: What happens after the BlackBerry Collaboration Service stops responding
  
• Scenario: What happens after the primary BlackBerry Dispatcher promotes a connection to a BlackBerry Collaboration Service