A critical component to any ArcIMS web site is the ArcIMS Application Server. All map service requests pass through the Application Server on their way to an ArcIMS Spatial Server. You can use multiple Application Server machines to help ensure that your site is always up and running or to help make more efficient use of your hardware resources. You can set up redundancy in two ways:

1. Failover - In this configuration, Application Server B is used if Application Server A fails to respond.
2. Round Robin - In this configuration, the first request goes to Application Server A, the second request to B, the third to A, and so on.

Both configurations, Failover and Round Robin, have their pros and cons. Failover is designed to ensure that requests are always channeled to a working Application Server. Round robin is designed to make efficient use of the system resources to handle high request volume. Choose the configuration that best suits your needs.

For details on setting up multiple ArcIMS Application Servers when using the Servlet Connector, see Step 2: Planning an ArcIMS site configuration in the ArcIMS Installation Guide, and look for the topic "Common site configuration scenarios".

After you have added additional Application Servers, you must administer services and servers using the Service Administrator.

For details on setting up multiple ArcIMS Monitors, see Step 3a: Installing ArcIMS in the ArcIMS Installation Guide, and look for the topic "Installing additional ArcIMS Monitors".