Summary Te run any eperating system in a virtual machine, an installation
should: Design new and existing application programs to operate efficiently
in a paging environment; that is, have them use VM/370 paging instead
of DOS/VS or as/vs paging. Reduce a virtual machine's I/O operations. Use VM/370 services for performance and communication, such as the VM/310 virtual machine options and VMCF. When running specific multiprogramming operating systems under VM/370 (such as DOS/VS or OS/VS), an installation should consider how that
system interacts with VK/370 -- especially when that system has a page
wait or I/O wait. To interact with these VK/370 provides VM/VS handshaking for certain DOS/VS and VS1 systems, and the diagnose
interface fer virtual operating systems, such as DOS/VS and OS/VS. Other areas to consider when running multiprogramming operating
systems under VK/370 are spooling, channel whether
to use multiple or alternate consoles, and the states or conditions of
virtual devices (dedicated, shared, and spooled). VK/370 also supports alternate paths, multiple-access virtual
machines, eperating systems using reser7e/re1ease, and the ASP virtual machine. Installations can also alternate between operating
systems under VK/370. While difficult to predict, performance of any virtual machine may be
impreved by the choice of hardware, operating system, and VK/370 eptiens. VM/370 also provides the INDICATE and MONITOR commands to
track and measure both VK/370 and virtual machine performance. VM/370 can help considerably throughout the system generation
process. Its biggest advantage is allowing an installation to generate
a system under VK/370 without disturbing production activity.
To allow virtual machines to access the VK/370 system, the VK/370 system requires a file of directory entries that contains one entry for
each virtual machine. Each directory entry contains a number of
directory control statements that define the virtual machine's
ccnfiguratien and operational characteristics to VM/370. Some directory
statements have unique considerations when running an operating system
in a virtual machine. There is an AUTOLOG facility to automatically
initiate large producticn operating systems with many I/O devices under V!1/370. 50 IBM VM/370 Operating Systems in a Virtual Machine
page of GC20-1821-3 As Updated April 1, 1981 by TNL GN25-0840 Section 2. VM/370 in a Virtual Machine
This section describes how to update and test a VM/370 system in a
virtual machine. After testing, use the DASD dump restore (DDR) program
to dUmp the virtual CP (VM/370) system to tape. Then, restore that
virtual CP system to the real system residence disk. After performing
these steps, an installation is ready to execute the new version of VM/370 with a minimum amount of real time. VM/370 Directory Definition
Before an installation can test VM/370 in a virtual machine, it must
first have a VM/370 directory entry for a VM/370 virtual machine. The
virtual directory need only specify a minimum number of users that are
sufficient to perform the testing. It is usually beneficial to define
an operator's virtual machine that is large enough and varied enough to
perform all necessary functions. This specification allows most virtual
testing to be done from one userid. It does not require several userids
to dial into this system to accomplish a test.
In the followinq sample directory entry, assume that TESTSYS is the
userid for this virtual machine. TESTSYS has the options and
configuration necessary to define a m1n1mum system for initializing VM/370 in a virtual machine. A sample VM/370 directory entry for TESTSYS would be: USER TESTSYS PASSWORD 512K ACCOUNT NUMBER BIN11 OPTION ECMODE REALTIMER CONSOLE 01F 3215 SPOOL C 2540 READER SPOOL D 2540 PUNCH SPOOL E 1403 LINK CMSSYS 190 190 R MDISK 330 3330 1 15 SYSWRK WR RPASS WPASS MDISK 331 3330 16 20 SYSWRK WR RPASS WPASS The USER statement defines the userid as TESTSYS, the password as PASSWORD, and 512K storage (the minimum amount of storage to load a
virtual VM/370 system).
The OPTION statement specifies the ECMODE and REALTIMER options,
which are required for the virtual machine to operate in extended
control mode and to wait for a timer interruption to continue
processinq.
The CONSOLE and SPOOL statements specify the console and spool
device addresses. These addresses must match the same addresses as
the real machine configuration. If that configuration is not .used
for the virtual system operation, they must match whatever
configuration is specified in the DMKRIO module.
The LINK statement specifies that this virtual machine may operate CMS, althouqh special considerations described later in this
section have to be used to operate eMS. section 2. VM/370 in a Virtual Machine 51
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