Job Entry Subsystem 2/3

The Job Entry Subsystem (JES) is a component of IBM's MVS (OS/VS2 R2 through z/OS) operating systems that receives jobs into the computer system, schedules them for processing, and controls their output processing. There is also a JES in OS/VS1, often referred to as JES1. While MVS/370's immediate predecessor, SVS, retained the spooling facilities of OS/360, most installations used the optional ASP Version 3 or HASP II Version 4. sometimes incorrectly referred to as HASP4; ASP V3 is available for OS/360 and HASP II V4 has been quite easily retrofitted to OS/360, even on systems which did not, and cannot support the System/370 instruction set.