Example of Workload Processing in An Active-Passive Server Setup

Each of these solutions uses one or more standby or "passive" servers,
which hold a replica of the main "active" database.

During normal processing,
the work-load is directed to the "active" server,
as shown in Figure 2-4a.

In the event of a failure of the "active" server,
the processing is transferred to the passive server and it becomes the active server,
as shown in Figure 2-4b.

Source:
Microsoft SQL 2005 Administrator's Companion, Page 41