name = z/OS
caption = The z/OS welcome screen as seen through a
terminal emulator. This interface is still available but Web access is common.
website = [http://www-1.ibm.com/servers/eserver/zseries/zos/ IBM: z/OS operating system]
family = z/OS
source_model = Mostly
latest_release_version = Release 10 (V1R10)
September 26, 2008
marketing_target = Enterprise / Mainframes
Monolithic kernel(uniquely hardware-assisted)
license = Proprietary monthly license charge (MLC); pricing available based on actual use (VWLC)
working_state = Current
z/OS is a
64-bit operating systemfor mainframe computers, created by IBM. It is the successor to OS/390, which in turn combined MVSand a number of related products.
z/OS offers many of the attributes of other modern operating systems, but also retains much of the functionality originating in the 1970s and 1960s, that is still often in daily use. This includes
CICS, IMS, DB2, RACF and SNA.
z/OS also runs 64-bit Java, supports UNIX (
Single UNIX Specification) APIs and applications, and communicates directly with TCP/IP. A complementary IBM operating system, z/VM, provides the management of multiple virtual systems ("guests") on the same physical mainframe. These new functions within z/OS and z/VM, and the Linux support, have encouraged development of new applications for mainframes. Many of them utilize the WebSphere Application Serverfor z/OS middleware.
Because there is only one version, releases are normally called "Release n", though more formally they are "Version 1 Release n" or "V1.n".
April 1, 2007, z/OS is only supported on 64-bit ( z/Architecture) mainframes. z/OS Release 5 was the last release to support ESA/390, a previous hardware architecture having 31-bitaddressing. Old applications are still supported in the same binary form, whether they use 31-bit or even 24-bitaddressing.
IBM markets z/OS as a flagship [IBM: Why System z for Business Integration? [http://www-03.ibm.com/systems/z/integration/advantages.html] ] operating system, suited for continuous, high-volume operation with high security and stability.
A lower-cost variant of z/OS, z/OS.e, is identical in code but runs with a startup setting that prevents execution of "classic" workloads such as the
COBOLand PL/Icompilers. z/OS.e was available for IBM z800, z890, and z9 BC mainframes. But z/OS.e ended with Release 8 and was withdrawn from marketing in October, 2007. [IBM System z New Application License Charges [http://www.ibm.com/common/ssi/fcgi-bin/ssialias?infotype=an&subtype=ca&appname=Demonstration&htmlfid=/897/ENUS207-006] ] It is replaced by the System z New Application License Charges (zNALC), which offers the full z/OS cheaper if used to serve new applications ("new workloads").
IBM reliably makes new releases of z/OS annually. Release 10 became generally available on
September 26, 2008(first announced on August 5, 2008).
Intelligent Resource Director
Linux on zSeriesfor a mainframe version of a popular operating system
OS/360for an ancestor from 1960s
* z/VSE for another mainframe operating system
* Parallel Sysplex
Resource Measurement Facility
* [http://www.ibm.com/servers/eserver/zseries/zos/ IBM: z/OS]
* [http://www.ibm.com/software/shopzseries IBM: Shop zSeries (ShopZ)]
* [http://www-03.ibm.com/servers/eserver/zseries/zos/bkserv/ IBM: z/OS Internet Library]
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