While having only a single Siebel Server is a common scenario for demonstration or development environments, there are several good reasons to deploy more Siebel Servers in other Siebel environments such as test or production environments.
Among these reasons are the following:
Scalability, load balancing, and performance considerations
Failover security
Deployment of application configurations with minimal downtime
The following diagram depicts a Siebel Enterprise with two Siebel Servers:
Both servers host the same object manager. Siebel Native Load Balancing is enabled, distributing the load evenly between the servers.
When the engineers at Siebel Systems drafted the first design documents in the early 90s, they had large global corporations with thousands of end users in mind. This is one of the reasons why the Siebel server infrastructure is so scalable. It is an easy computation that the more servers we have, the more end users we can support...