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

CP provides each of these with virtual device support and virtual
storage. The operating systems themselves execute as though they are
ccntrolling real devices and real storage, but they must not violate any
of the restrictions listed in VML37Q flanRing with the exception of OS/pCP, all the batch or single-user systems are
multiprogramming systems. However, when operating in a virtual machine
under VM/370, the user has the choice of running either multiple
partitions in one virtual machine similar to stand-alone operation or
single partitions in multiple virtual .achines. When running multiple
partitions in one virtual machine, mUltiprogramming and unit record
sFooling is done by both the operating system and This may
decrease the overall efficiency of the virtual machine. When running
single partitions in multiple virtual machines, the need for multiple
virtual stcrage spaces places a burden on auxiliary storage. However,
using shared systems reduces this burden.
Each multiple-access system operates in one virtual machine and supports
multiple interactive users. The multiple-access virtual machine must
first gain access to VM/370 (by using the LOGON command). Subsequently,
interactive users can connect to the multiple-access system (either by
using the DIAL command or by using a terminal on a dedicated line).
Ccmmunication between the two is carried out by using the command
language of the multiple-access system.
The conversational monitor system (CMS) is a component that
Frovides a wide range of conversational and time-sharing facilities.
Together with the control program of V8/370, it provides a time-sharing
system suitable for direct problem solving and program development. Ey
using CMS, a virtual machine user can create, update, and manipulate
files. The user can also compile, test, and execute problem programs.
The CMS interactive capabilities are extended to DOS/VS users by using either the CMSjDOS environment or CMS. For OS/VS users, a
combination of CMS commands and CMS simulation of os macro instructions Frovides similar interactive capabilities. For information on using the eMS v1rtual machine, refer to and VML11Q OTHER PROGRAMS AND SYSTEMS For information about other programs and systems that have been used
under VM/370, request information on Installed Oser programs (lOPs) and
Field Developed Prograas (FDPs) from your local IBM branch office. For
a list of IUPs, refer to VML170 §uide. Section 1. General Considerations 3