Section 1. General Considerations
The Virtual Machine Facility/310 (VM/370) provides an easy, convenient
way to use a single terminal to run other operating systems, such as DOS/VS, OS/VS1, or 05/VS2. with VM/310, system programmers can test a
new applicaticn program with an operating system, or they can develop
and test new operating system releases. They can do this work on any
shift, and they can do it isolated from any work that is running
concurrently elsewhere in the system. This isolation is done by the use
of a virtual machine.
A virtual machine is a functional equivalent of an IBM System/310 computing system. Each virtual machine has the functional equivalent of
a real processor, main and auxiliary storage, and I/O devices. Because VM/310 only simulates these functions, this simulated machine is
referred to as a "virtual" machine. V8/310 manages the functions of a
real IBM System/310 in such a way that virtual machines are available to
multiple concurrent users.
Before running any operating system in a virtual machine, an
installation should consider: How can application programs operate efficiently in a virtual
machine? How it can reduce a virtual machine's I/O operations? Which services are available for performance and communication for
both VM/310 and a virtual machine? What special considerations are there for multiprogramming operating
systems under VM/310, such as DOS/VS or OS/VS? What operating system functions and devices does VM/310 support and
not support? How to genera te a n opera ting system under VM/310? How can virtual machines access the V8/310 system?
In answering these questions, this publication assumes that readers
have a basic understanding of V8/310 concepts and functions as described
in the It also assumes that they have a basic
understanding of whatever operating system they are running under VM/370. What virtual machine resources and operating systems can be used
under VM/370? VIRTUAL MACHINE RESOURCES Virtual machine resources are either shared among users or allocated to
users alternately for a specified time period. The resources to be
allocated to any particular virtual machine are specified in the V8/310 directory entries for that virtual machine. The directory entries for
all virtual machines make up the V8/310 directory file that is usually Section 1. General Considerations 1
located on the '8/370 systea residence volume. When a user obtains
access to the V8/370 system, a virtual machine is created based upon
that user's directory entry. The user can then load any of the
supported operating systems and begin processing.
For a virtual machine to begin processing under V8/370, what
functions does V8/370 itself provide?
The V"/370 system has four components: (£R): CP controls the resources of
such that multiple virtual machines or computing systems
exist.
a computer
appear to C8S provides a wide range of
conversaticnal and time-sharing facilities. By using CMS, an
installation can create and manage files, and compile, test, and
execute problem programs. §YQ§I§te! spool files between V8/370 users and remote telecommunication lines. RSCS transfers
locations over £on!fQ! IPCS provides VM/370 problem analysis and management facilities, including problem report
creation, problem tracking, and CP abend dump analysis.
For an overview of these VIRTUAL MACHINE OPERATING SYSTE8S V8/370 concepts, refer to While the control program of V8/370 manages the concurrent execution of
the virtual machines, it is also necessary to have an operating system manage the work flow within each virtual machine. Because each virtual machine executes independently of other virtual machines, each one can
use the same operating system, a different operating system, or
different releases of the same operating system.
The operating systems that can execute in virtual machines are:
Ba tch or DOS DOS/VS DOS/VSE as/pcP OS/"FT OS/MVT OS/VS1 OS/VS2 SVS OS/VS2 MVS OS-ASP RSCS L VM/370 Time Sharing Option of as DOS/VSE with VSE/ICCF (5746- TS1) 2 IBM 1M/370 Opera Systems In. Virtual Machine
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