When an application is deployed or updated, it is often required to restart the BizTalk host instance that the application runs in, to ensure the DLLs are reloaded correctly. If all the orchestrations in the hub were running in the same host instance, this would interrupt the processing of all the business processes.

If a separate host is created for each module, that host instance can be restarted without affecting any other business processes. There is also an option for finer configuration of host instances, to allow high priority business processes to run across multiple servers and to limit lower priority heavy batch processes to fewer servers. This will ensure that there are always resources available for the higher priority operations.