JES2JES3

JES2 and JES3 are IBM mainframe Job Entry Subsystems that control the submission, queuing, and initiation of batch and interactive jobs on IBM’s MVS-derived operating systems, including OS/390 and z/OS on System/390 and IBM Z hardware. The term JES2JES3 is informal shorthand used in some discussions to refer collectively to the two subsystems or to mixed environments where both are present. It is not an official product name.

JES2 is the standard local job-entry subsystem used on most installations. It handles local job submission, queuing, dispatch, and spooling on the member’s own system. It supports local printers, multiple class-based priorities, and straightforward configuration for a single sysplex member.

JES3 is designed for cross-system operation across a sysplex, allowing a central or shared spool and cross-system job routing. It is used in very large environments where multiple MVS-family systems must process jobs from a common queue and share devices and resources. JES3 communicates across systems via the XCF (Cross-System Coupling Facility) infrastructure and provides mechanisms for cross-system locking and dispatch. In practice, many shops use JES2 on the majority of systems and reserve JES3 for specialized, high-scale workloads; others deploy JES3-wide configurations in multi-system environments.

Because JES2 and JES3 operate differently, administrators planning a sysplex or migration should understand the impact on job scheduling, security, and spool management. The double configuration is sometimes referred to as “JES2/JES3” in vendor notes and user discussions, but guidance and support are provided in IBM documentation under each subsystem.