VSE (operating system)
| Company type | Operating system |
|---|---|
| Industry | Computer software |
| Predecessor | DOS/360, DOS/VS, DOS/VSE, VSE/SP, VSE/ESA, z/VSE |
| Founded | 1965 |
| Headquarters | United States |
| Products | Operating system software for IBM mainframes |
| Website | www |
VSEn (Virtual Storage Extended) is an operating system designed for IBM mainframe platforms, representing the most recent evolution in the DOS/360 family that originated in 1965. It is less prevalent than z/OS and primarily deployed on smaller-scale mainframes.
The operating system DOS/VSE was introduced in 1979 as the follow-up to DOS/VS, succeeded by VSE/SP releases 1 (1983) and 2 (1985). During the late 1980s, there was concern among VSE users that IBM might phase it out in favor of MVS, but IBM continued its enhancement efforts. In February 2005, IBM unveiled z/VSE as the next generation after VSE/ESA 2.7, aligning it with the System z branding for its mainframe series.
In June 2021, 21st Century Software Inc acquired a license from IBM for the z/VSE source code to advance development and reintroduced it under the name VSEn.
Overview
Initially, DOS/360 operated with 24-bit addressing. The introduction of VSE/ESA brought 31-bit addressing support as hardware capabilities improved. IBM launched z/VSE Version 4 in 2007, which required 64-bit z/Architecture hardware and enabled 64-bit real mode addressing. Starting with z/VSE 5.1 in 2011, features such as 64-bit virtual addressing and memory objects exceeding 2 GB were incorporated.
Job Control Language (JCL)
The principal batch processing mechanism for VSEn continues to be a Job Control Language (JCL) that follows the positional-parameter format characteristic of earlier DOS systems. Additionally, there is a dedicated interface designed for system console operators.
Beyond batch
While traditionally offering user interfaces via 3270 terminals, most VSEn environments now provide access to applications through Web browsers. TCP/IP connectivity is offered as an optional feature by two vendors supplying comprehensive protocol stacks—one supporting only IPv4, and another supporting both IPv4 and IPv6. IBM also delivers the Linux Fastpath solution, which leverages IUCV sockets or Hipersockets to link VSEn with a Linux guest running on the mainframe, thereby enabling utilization of Linux’s native TCP/IP stack.
IBM advises deploying z/VSE alongside Linux on IBM Z within a single physical machine using a z/VM-mode logical partition (LPAR). This configuration offers a complementary 64-bit application environment that expands z/VSE’s capabilities through Hipersockets and middleware integration. The enterprise transaction processing system CICS remains widely adopted by VSEn customers and supports modern features such as Web services. IBM Db2 is also available and commonly implemented.
Device support
VSEn is compatible with ECKD, FBA, and SCSI device types. Initial Fibre Channel support for SCSI storage in z/VSE 3.1 was limited to IBM’s Enterprise Storage Server (ESS), System Storage DS8000, and DS6000 models; these constraints were lifted with version 4.2, expanding compatibility to include IBM Storwize V7000, V5000, V3700, and V9000 systems.
See also
- z/OS
- z/TPF
- z/VM
- History of IBM mainframe operating systems#DOS/VS
- History of IBM mainframe operating systems