Identity Manager requires a lightweight gateway to manage resources that cannot be directly accessed from the server. These include systems that require client-side API calls that are platform specific. For example, if Identity Manager is running on a UNIX-based application server, the ability to make NTLM or ADSI calls to managed NT or Active Directory domains is not possible. Because Identity Manager requires a gateway to manage these resources, it is important to ensure that the Identity Manager Gateway is made highly available.
To prevent the Gateway from becoming a single point of failure, Sun recommends having multiple machines running a Gateway instance. A network routing device should be configured to provide failover if the main Gateway instance dies. The failover device should be setup for sticky sessions and use a simple round robin scheme. Do not place the Gateways behind a device that load balances! This is not a supported configuration and will cause certain Identity Manager functions to fail.
All Windows domains managed by a Gateway must be part of the same forest. Managing domains across forest boundaries is unsupported. If you have multiple forests, install at least one Gateway in each forest.
Win32 monitoring tools can be configured to watch the gateway.exe process on the Win32 host. In the event that gateway.exe fails, the process can be automatically restarted.