Shortest job next (SJN), also known as Shortest Job First (SJF) or Shortest Process Next (SPN), is a scheduling policy that selects the waiting process with the smallest execution time to execute next. SJN is a non-preemptive algorithm. Shortest remaining time is a preemptive variant of SJN.
Shortest job next is advantageous because of its simplicity and because it maximizes process throughput (in terms of the number of processes run to completion in a given amount of time). It also minimizes the average amount of time each process has to wait until its execution is complete. However, it has the potential for process starvation for processes which will require a long time to complete if short processes are continually added. Highest response ratio next is similar but provides a solution to this problem.
Shortest job next can be effectively used with interactive processes which generally follow a pattern of alternating between waiting for a command and executing it. If the execution of a command is regarded as a separate "process", past behaviour can indicate which process to run next, based on an estimate of its running time.
Shortest job next scheduling is rarely used outside of specialized environments because it requires accurate estimations of the runtime of all processes that are waiting to execute. Estimating the running time of queued processes is sometimes done using a technique called aging.[1]