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

ERROR RECORDING AND ANALYSIS The operating systems commonly run
write error records to the error
virtual machine VK/370 intercepts
own error recording cylinders.
operating systems reside in this
To access the recorded data, use
information about error recording UNSUPPORTED DEVICES in virtual machines all use SVC 76 to
recording data sets. However, in a SVC 76 and records the error on its
Therefore, error records from all
one centralized error recording area.
the CKS CPEREP command. For further
and CPEREP, refer to OL!SEg Virtual machine users may be able to use I/O devices that Ve/370 does
not support. An unsupported device is a device type that is not listed
in the DEVTYPE operand of the RDEVICE macro instruction. To use an
unsupported device, a user must attach or dedicate the device to a
virtual machine. A dedicated device is one that is not shared among
users, but is used exclusively by one user. However, VM/370 supports
these dedicated devices only under these conditions: • No timing dependencies exist in the device or the program. • No dynamically modified channel programs exist in the access method,
except when OS ISAK or OS/VS TCAK Level 5 are used. • No special functions need to be provided by • None of the other CP restrictions are violated. (Refer to the VM/370 restrictions list in the • The device is generated into the VK/370 nucleus (by using the RDEVICE macro instruction with the appropriate CLASS operand). I/O devices that are part
require real device equivalents.
of a virtual machine's configuration
However, exceptions to this rule are: • Unit record devices, which VK/370 can simulate by using spooling
techniques. • Virtual 2311 disks which VK/370 can map onto 2314 or 2319 disks. One to two full 2311 units can be mapped onto a 2314 or 2319 disk in this
manner. • When 3350 disks are used in 3330-1 or 3330-11 compatibility mode.
4 IBM V3/310 operating Systems in a Virtual Machine