Free tools Windows power users keep installed
One-click scans. No signup required.
iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A job entry subsystem (JES) is a z/OS component that receives jobs, queues and schedules them for processing, and manages their output. It prepares work before a program runs and handles output afterward; the z/OS base control program manages the job during execution.
What does a job entry subsystem do?
IBM describes three core JES functions: accepting jobs into z/OS, scheduling them for processing, and controlling output processing. A job can enter the system in several ways, including an ISPF SUBMIT command, a network connection, a card reader, or a running program using the JES internal reader. JES manages queues for submitted jobs and their output.
JES coordinates with initiators, which process JCL and run batch jobs in an address space. JES does not itself execute the application program. A useful way to picture the division is: JES receives and queues the work, z/OS runs it, and JES manages the resulting output. IBM’s JES overview and its z/OS 3.2 JES2 introduction describe these roles.
How does JES use spooling?
Spooling is the use of auxiliary storage to buffer job input and output streams while work is being processed. This lets a job’s input or output be held for later handling rather than requiring a device, such as a printer, to be available at the exact moment the job runs.
#1 Best Overall
- Murach's Mainframe COBOL
- Mike Murach & Associates
- ABIS BOOK
JES can queue output for a printer or retain it on spool for an output manager to retrieve. Input can also be buffered for jobs. IBM’s CICS interface to JES documentation describes spool files as buffers between the job that creates output and later device processing.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.What is the difference between JES2 and JES3?
IBM identifies JES2 and JES3 as the two JES types. They perform many similar functions, including job intake, scheduling and queue management, and output handling. IBM’s overview says most installations use JES2, but it does not give a current adoption percentage. The available documentation also does not establish a universal reason to select one over the other or support a detailed, current feature-by-feature comparison.
For an individual z/OS environment, the practical context is the subsystem already in use at that site. IBM’s batch-job processing overview explains the role of JES in the flow of work.
Quick Recap
Where does JES fit in a batch job’s lifecycle?
- Submission: A user or system submits a job, for example with ISPF’s
SUBMITcommand or through an input source such as a network connection or internal reader. - Queueing and scheduling: JES places work in queues and coordinates with an initiator that processes JCL and starts the batch job.
- Execution: The application runs under z/OS. The base control program manages the job during this stage.
- Output handling: JES manages the job’s output, which can be queued for a device or left on spool for later retrieval.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
