An IBM® Integration Bus integration node supports any number of integration servers, there is no finite limit. Practical limitations such as the amount of real memory or swap-space, do force a maximum limit to ensure continued levels of service.
Large systems typically have under 100 integration servers. A broker with over 100 integration servers is considered 'very large', and it is recommended to review the strategy that is used to create integration servers and assign message flows to them. The number of integration servers that are used does not affect the amount of either virtual memory or real memory that is used by an individual integration server. However, the number of integration servers does have a strong effect on the amount of real memory that is required by the integration node. It is therefore necessary balance business requirements against performance requirements when you calculate how many integration servers are required.
Just because an integration server can host hundreds of message flows, it is not always a good idea for it to do so. For example, if the integration server fails, many applications are lost until the integration server is restarted. And that restart time increases significantly the more message flows that the integration server hosts.
Whichever strategy you use, plan for future expansion and ensure that the topography still works when hundreds more services are added. Decisions that are made in 'the early days' often do not scale when hundreds more services are added, and the demand for more real memory becomes a problem.