Section 3. DOS/VS In a Virtual Machine
This section uses the term "DOS/VS" as a generic expression. It
represents any or all of the DOS, DOS/VS, and DOS/VSE system control
programs unless specified otherwise. When loading DOSjVS into a virtual machine running under the
terminal becomes the DOS/VS operator console, and the user is
responsible for entering all the commands and responses normally
required of the operator.
The three basic techniques to use when running DOS/VS in a virtual
machine are: 8 Run DOS/VS in batch mode. The terminal is the operator console, and
other users may submit jobs either through the real system virtual
card reader or from the virtual card punches of other userids. • Use the IPt command to alternate between using DOS/VS and in a
single virtual machine,. Use CMS to prepare a job stream for DOS/VS, use DOS/VS to execute the job stream, and use CMS to check the
output. • tog onto a userid and load DOS/VS. Once it is running, disconnect
from that userid and log onto another userid while the DOS/VS userid
continues working. To check on the status of DOS/VS, disconnect from
the current virtual machine and reconnect the DOS/VS virtual machine.
Before discussing these three techniques in greater detail, the user
must understand how to: • Generate DOS/VS to run in a virtual machine • create VM/370 directory entries for DOS/VS 'virtual machines • Access the DOSjVS system residence volume • Ensure that the proper I/O devices are attached to the DOS/VS virtual
machine • IPt and operate DOS/VS under VM/370 System Generation Recommendations When generating DOS/VS to run in a virtual machine, an installation
should have these primary objectives: • Tc reduce the number of 510 instructions issued by DOS/VS, including
those issued for DOS/VS paging I/O operations • To avoid double CCW translation
To meet these
generates both
objectives, an installation VM/370 and DOS/VS. needs to consider how it Section 3. DOS/VS in a Virtual Machine 69

r , The fcllowing recommendations have been made by users who runl I DOS/VS in a virtual machine under VM/370. As such, thesel Irecommendations have not been submitted to any formal IBM tests.1 IPrier to any implementation, an installation should evaluate their I lusefulness in its own configuration. I VM/370 RECOMMENDATIONS When generating VM/370 for a DOS/VS virtual machine, note the following
recommendations: IPL time can be reduced by saving any operating system after the
generated operating system has been loaded on VM/370. For more
information about generating saved systems, refer to the DOS/VS Release 34 with the Advanced Functions-DOS/VS program Product (Program No. 5746-IE2) uses VM/VS handshaking. The use and efficiency
of DOS/VS with handshaking is similar to using VS1 handshaking with VM/370. For further details, refer to the appropriate DOS/VS program
product publications. DOS/VSE with the VSE/Advanced Functions program Product (5746-XES) uses VM/VS handshaking (also known as the DOS/VSE-VM/370 linkage
facility). The use and efficiency of DOS/VSE with handshaking is similar to using VS1 with handshaking. For further details, refer to GC33-6106.
Tc initialize a DOS/VS minidisk for use under VM/370, the IBCDASDI service program be used. If the whole disk is DOS/VS, any DOS or OS disk initialization program may be used. 70 IBM iM/370 Operating systems in a Virtual Machine VM/370 used by