Most business methods and processes are invoked from clients in direct response to client activities, but the system is also capable of executing jobs in the background, separated from user interactions. It is quite common that large, perhaps long-running tasks runs in the background. Depending on implementation, such background calls can execute either in the database tier or in the middle-tier. End users can submit such jobs for background execution, but jobs can also be scheduled to run at a later time or repeatedly.