The simplest topology is an enterprise service bus consisting of a single server, as created if you install WebSphere ESB in a stand-alone server profile.
In a single-server enterprise service bus, the SCA.SYSTEM bus has the one server as its only bus member. When you install a mediation module into WebSphere ESB, the queue destinations used by the module are defined on that bus member. These queue destinations are used by the SCA runtime exploited by the mediation module as a robust infrastructure to support asynchronous interactions between components and modules.
The server hosts a messaging engine that provides the service integration technologies used by the queue destinations and the processing of requests.
In a stand-alone profile, there can be only one messaging engine in a bus, a topology that is adequate for some scenarios.
A single messaging engine might not be adequate if the number of client connections becomes excessive, if the rate of message throughput cannot be sustained by the one messaging engine, of if the size of messages needs more space than the one messaging engine can provide in its data store.
To add more than one messaging engine to a service integration bus, you need to use a profile for a managed node in a deployment manager cell.
The easiest way to create a stand-alone server is to perform a Complete installation. With a Complete installation, you get a stand-alone server profile named default with a server named server1.