|OS family||DOS/360 and successors|
|Source model||Closed source|
|Latest release||IBM z/VSE V6.1 / October 5, 2015|
|Marketing target||IBM mainframe computers|
z/VSE (Virtual Storage Extended) is an operating system for IBM mainframe computers, the latest one in the DOS/360 lineage, which originated in 1965. It is less common than prominent z/OS and is mostly used on smaller machines. Primary z/VSE development occurs in IBM's Böblingen labs in Germany.
DOS/360 originally supported 24-bit addressing. As the underlying hardware evolved, VSE/ESA acquired support for 31-bit addressing. IBM released z/VSE Version 4 in 2007. z/VSE Version 4 requires 64-bit z/Architecture hardware and supports 64-bit real mode addressing. With z/VSE 5.1 (available since 2011) z/VSE introduced 64 bit virtual addressing and memory objects (chunks of virtual storage), that are allocated above 2 GB. The latest shipping release is z/VSE 6.1.0 - available since November 2015, which includes the new CICS Transaction Server for z/VSE 2.1.
IBM recommends that z/VSE customers run Linux on z Systems alongside, on the same physical system, to provide another 64-bit application environment that can access and extend z/VSE applications and data via Hipersockets using a wide variety of middleware. CICS, one of the most popular enterprise transaction processing systems, is extremely popular among z/VSE users and now supports recent innovations such as Web services. DB2 is also available and popular.
Job Control Language (JCL) is z/VSE's batch processing interface. There is also another, special interface for system console operators. z/VSE, like z/OS systems, had traditionally supported 3270 terminal user interfaces. However, most z/VSE installations have at least begun to add Web browser access to z/VSE applications. z/VSE's TCP/IP is a separately priced option for historic reasons, and is available in two different versions from two vendors. Both vendors provide a full function TCP/IP stack with applications, such as telnet and FTP. One TCP/IP stack provides IPv4 communication only, the other IPv4 and IPv6 communication. In addition to the commercially available TCP/IP stacks for z/VSE, IBM also provides the Linux Fastpath method which uses IUCV socket connections to communicate with a Linux guest, also running on the mainframe. Using this method the z/VSE system is able to fully exploit the native Linux TCP/IP stack.
The last VSE/ESA release - VSE/ESA 2.7 - is no longer supported since February 28, 2007. z/VSE 3.1 was the last release, that was compatible with 31-bit mainframes, as opposed to z/VSE Version 4 and 5. This version was supported to 2009. z/VSE Version 4 is no longer supported since October 2014 (end of service for z/VSE 4.3).
For VSE/ESA, DOS/VSE, VSE/SP, see History_of_IBM_mainframe_operating_systems#DOS/VS