Documentation of Operating Systems and Developers

MVS, OS/390, z/OS operating system

MVS (Multiple Virtual Storage) is the operating system which is developed by IBM in the sixties and supports POSIX. MVS was developed further from MVT operating system and extended by many functions like the use of virtual memory. It is used in IBM mainframes like the system /370 and system /390, needs low hardware requirements and convinces by a high stability in long-term operating mode. It primarily was used for providing of resources for terminal connections. JCL (Job Control Language) is used for the Batch processing, within zOS TSO/E (Time Sharing Option/Extended) serves the receipt of orders. As a dialog application ISPF (Interactive System Productivity Facility) helps at the development of the own programming and documentation of dialog and batch applications. At the beginning it was a 16-bit operating system and was developed further for the 32-bit of processing. With the version MVS/ESA the addressability for RAM and hard disk storage was extended. After the renaming of MVS into OS/390 the TCP/IP support was added into the release. This operating system now is called z/OS and his special char "z" at the beginning of "z/OS" stands for the good suitability of IBM servers of the zSerie like the z900. Now it is offering 64-bit addressing of memory too.

With the Hercules open source software it is possibly to emulate an IBM mainframe. Last update was with version 3.03 in December 2005, the emulator runs under different operating systems.

Abbreviations
MFT = Multiprogramming with fixed number tasks
MVT = Multiprogramming with variable number tasks
SVS = Single Virtual Storage
MVS/XA = MVS with extended architecture
MVS/ESA = MVS with enterprise system architecture

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