There are a series of modes that Adaptive Server runs through during high availability. There are two types of modes, stable and transitional. A stable mode is a system state in which Adaptive Server can exist for an extended period of time, such as the day-to-day operation of Adaptive Server.
Stable modes include:
Single-server mode
Normal companion mode
Failover mode
Suspended companion mode
Failback mode, which is transitional, occurs when Adaptive Server shifts from a failover mode to a normal companion mode, and is typically of very short duration. The movement that the primary companion makes while changing modes is shown in Figure 4-1:
Figure 4-1: Modes of operation for high availability
Before you can configure two Adaptive Servers as companions, both must be in single-server mode, which is the default mode of a newly installed Adaptive Server after running installhasvss. After you configure the Adaptive Servers as companions, they are in one of three stable modes:
Normal companion mode
Failed-over mode
Suspended companion mode
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