zVSE

zVSE is IBM's midrange mainframe operating system for IBM System z hardware. It is a member of the VSE family designed for reliability, modest footprint, and straightforward administration in small to medium enterprise environments. zVSE preserves the lineage from DOS/VSE and its successors and is presented as the System z option for customers who require a compact but capable mainframe operating system.

The DOS/VSE lineage began in the 1980s as an evolution of DOS/VS for IBM mainframes. It later evolved into VSE/ESA for ESA architectures and was eventually renamed z/VSE to reflect the System z platform. IBM has continued to maintain zVSE as a distinct operating system with periodic releases that add hardware support, performance improvements, and interoperability features while preserving application compatibility with existing VSE software.

zVSE provides batch processing, online job entry, and data management facilities typical of mainframe environments. It includes support for network services such as TCP/IP and for IBM I/O devices, and offers development and administration tools, scripting capabilities, and optional components for time-sharing and terminal access. The operating system emphasizes stability, memory management, and robust I/O handling, along with mechanisms for backup, recovery, and availability in production settings.

It runs in logical partitions on IBM Z hardware and can coexist with other operating systems, including Linux on System z, on the same machine. System Z hardware features for virtualization and reliability are leveraged by zVSE, while data and peripherals can be managed through standard IBM interfaces and third-party software ecosystems.

zVSE remains part of IBM's z/Software family and is used by organizations seeking a lightweight mainframe OS with compatibility to older applications.