The job manager (JM) offers a single point of contact for applications to request necessary resources. It hides from the application the complexity of managing the resources that have been allocated by the system manager to a particular job.
When a job is initiated, the job manager locates system managers (by using either the Prospero Directory Service if available or a configuration file) and sends resource requests. If the response from the system manager is affirmative, then the job manager allocates the resources to the tasks in the job and contacts the node manager for each resource in order execute the tasks on the appropriate processors. If a system manager refuses the request, for example when the job manager is not authorized to make the request or when there are no resources available, then the job manager contacts other system managers which can satisfy its request.