!!! Overview 
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions. [2]

!! [External Security Managers (ESM)]
On z/OS there are three primary [External Security Managers (ESM)] There is a [ZOS BIDIRECTIONAL DRIVER] that will work with most of the [External Security Managers (ESM)] on [{$pagename}].!! More Information
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[#1] - derived from information provided at [http://en.wikipedia.org/wiki/ZOS] retrieved 2012-10-13
[#2] - [http://en.wikipedia.org/wiki/ZOS]