The JobAgentJoin tracks the same data as a JobStatus object. Each time the job's Status is updated on the Agent, the JobAgentJoin on the Master is updated to reflect the same data. 

Prior to adTempus 3.0, jobs were linked to agents by creating JobAgentJoin objects. Beginning with version 3.0, jobs are associated with JobQueues, which are in turn associated with Agents. A job can no longer be directly associated with an Agent: JobAgentJoin objects cannot be modified, and the job's RemoteAgents collection is read-only. 

JobAgentJoin objects are created automatically by adTempus for each Agent that the job's Queue is linked to.