Introduction

z/OS is a 64-bit operating system for mainframe computers, created by IBM. It is the successor to OS/390, which in turn followed MVS and combined a number of formerly separate, related products. z/OS offers the attributes of modern operating systems but also retains much of the functionality originating in the 1960s and each subsequent decade that is still found in daily use.

This is my daily sandbox where I play with IMS, CICS, REXX, CLIST, ISPF, TSO/E, JCL, CA7, etc.

Like Linux, z/OS has a monolithic kernel. A monolithic kernel is a kernel architecture where the entire operating system is working in the kernel space and alone as supervisor mode. This makes for a fast, secure and efficient OS. There are three types of kernel architectures:

• Monolithic (eg. Linux and z/OS)
• Mircrokernel (eg. Windows XP, Vista and 7)
• Hybridkernel (eg. Mac OS X)