* IBM PROGRAMMING INFORMATION OCTOBER 1981 *
* IBM PROGRAMMING INFORMATION *
* for Europe, the Middle East *
* IBM PROGRAMMING INFORMATION and Africa. *
* This document is provided as general customer information *
* only. IBM products and services which are announced and *
* available in your country can be ordered under the applicable *
* standard agreements, terms, conditions and prices in effect *
* at the time. For further information please contact your *
* local IBM representative. *
VM/XA MIGRATION AID
The VM/XA Migration Aid is being provided for the MVS user who
will be migrating to MVS/XA. It allows a 3081 user to logically
partition the dyadic processor between the MVS/SP prefered
virtual machine and the MVS/XA virtual machines. The VM/XA
Migration Aid operates on 3081 processors, models D16, D24, D32,
K16, K24, and K32 in the Extended Architecture mode. It
supports concurrently, one MVS/SP preferred virtual machine and
one or more MVS/XA virtual test machines, major test and
debugging facilities, and 32 megabyte virtual S/370 machines for
MVS/SP. VM/System Product CMS will be supported only to allow
servicing of this product. The primary objectives of the VM/XA
Migration Aid are:
o Maximize performance for the MVS/SP preferred virtual
o Support one or more MVS/XA test machines with extended test
This product will provide CMS capabilities to support only the
VM/XA Migration Aid Installation, service, and MVS/XA conversion
requirements. It is not intended to support general CMS users.
No performance evaluation tools, program products, or networking
capabilities will be available for use on this system.
The VM/XA Migration Aid will have the following features:
o Extended Architecture Support
- Large Real Storage
- Large Virtual Storage
- New Start Interpretive Execution Instruction
- New Channel Support
o MVS/SP Preferred Virtual Machine
- Preferred Virtual Machine
- Set Address Limit
- Dedicated Processor
- Dedicated Processor I/O
- Preferred Virtual Machine Recovery
o System Programmer Test Facilities
- Virtual Multiprocessing
- Debugging Facility
- Trace Facility
EXTENDED ARCHITECTURE SUPPORT
The VM/XA Migration Aid will exploit the extended architecture
by providing support for extended real storage, extended virtual
storage, hardware assisted emulation for S/370 and extended
architecture virtual machines, and the new extended architecture
channels. For a more detailed description on the extended
architecture, see the appropriate announcement letter.
LARGE REAL STORAGE: The VM/XA Migration Aid will support all
real storage configurations allowed by the extended architecture
(extended architecture provides for offerings of real main
storage up to two gigabytes).
LARGE VIRTUAL STORAGE: Extended architecture includes a new
mode which allows the use of 31-bit storage addresses and
one-megabyte storage segments. Extended architecture virtual
machines can define storage sizes up to 999 megabytes of storage.
The System/370 Extended Architecture virtual machine can use CCWs
in either S/370 format (format 0) or extended architecture format
(format 1) for its I/O operations. Translated channel programs
are always in extended architecture format.
The VM/XA Migration Aid will allow MVS/370 virtual machines to
define storage sizes up to 32 megabytes.
START INTERPRETIVE EXECUTION: A new instruction, Start
Interpretive Execution, is associated with the extended
architecture emulation facility. The emulation facility is used
by the VM/XA Migration Aid to provide hardware support for
several areas of virtual machine operation, such as: interval
timer, prefixing, address translation, and privileged instruction
The VM/XA Migration Aid will dispatch all virtual machines by
executing the Start Interpretive Execution instruction. The
virtual machine receives control in emulation mode and will
continue to execute in this mode until an interruption or
interception condition occurs.
The VM/XA Migration Aid also simulates the Start Interpretive
Execution instruction to allow the VM/XA Migration Aid to be
tested and serviced in a virtual machine.
NEW CHANNEL SUPPORT: The VM/XA Migration Aid will support the
new extended architecture channel interface. At the control unit
interface, 3081 channels are similar to System/370 channels.
However, at the programming interface, 3081 channels permit the
offloading of some function from the SCP to the channels. Many
of the System/370 channel functions have been replaced with new
ones that are MP and performance oriented. The hardware now
handles the alternate path and I/O queueing management.
The I/O supervisor of the VM/XA Migration Aid will use new
extended architecture I/O instructions in order to communicate
with the channels. In the extended architecture, interrupts are
recognized by class instead of by channel. There is no software
association of devices to control units or channels. Subchannels
are the addressable units in extended architecture and represent
individual devices. The new extended channels use new CCW
formats allowing addressing up to two gigabytes.
MVS/SP PREFERRED VIRTUAL MACHINE
PREFERRED VIRTUAL MACHINE: Preferred virtual machine means that
the preferred virtual machine executes with minimum interpretive
execution. The preferred virtual machine derives performance
benefits from a one to one virtual to real storage addressing.
The size of this preferred area is specified in megabyte
increments and physically begins at absolute zero of real
Note: Only MVS/SP version 1 (release 1 with enhancement and
release 3) is supported as the preferred virtual machine.
SET ADDRESS LIMIT: The integrity of the preferred virtual
machine is enhanced by the VM/XA Migration Aid use of the Set
Address Limit instruction. Using the Set Address Limit
instruction will cause the System/370 Extended Architecture
channel hardware to restrict I/O operations for dedicated devices
for the preferred virtual machine below its boundary, and
restrict for all other I/O above the boundary.
VIRTUAL S/370 I/O: The VM/XA Migration Aid supports S/370
architecture virtual machines, with all S/370 I/O operations
being automatically intercepted out of Start Interpretive
Execution. The virtual I/O simulation routines will recognize an
S/370 virtual machine and convert all of its I/O from S/370 to
System/370 Extended Architecture I/O operations. The S/370
virtual machine will have no knowledge of the extended
architecture processor on which it is running as the virtual I/O
simulator will maintain the S/370 interfaces. Virtual S/370 I/O
will be simulated as if each virtual device is on a non-shared
MASTER/DEDICATED MULTIPROCESSING SUPPORT: Master/Dedicated MP
support provides a multiprocessing environment where the 'master'
processor performs most VM/XA Migration Aids of the Control
Program (CP) work, and then runs virtual machines when all
control program work is completed. The 'dedicated' processor is
used to run only the preferred MVS/SP V1 virtual machine.
DEDICATED PROCESSOR: With Dedicated Processor support, the
MVS/SP preferred virtual machine is run in the 'dedicated'
processor and all other virtual machines are run in the 'master'
processor. Dedicated Processor support therefore eliminates all
contention from the other virtual machines for that processor's
compute power. If the 'dedicated' processor is not used to run
an MVS/SP preferred virtual machine, that processor will be
placed in an enabled wait state.
DEDICATED PROCESSOR I/O: The preferred virtual machine will have
a 'fast path IOS' to handle most S/370 SIOF initiation and I/O
interrupts without having to go to the 'master' processor.
This is done in a Master/Dedicated MP system by devoting an
interrupt subclass to the dedicated devices of the preferred
virtual machine. By running the preferred virtual machine on the
dedicated CPU enabled only for the dedicated interrupt subclass,
the operating system can eliminate the overhead of stacking and
unstacking I/O interrupts for other virtual machines and can
avoid CPU switching.
PREFERRED VIRTUAL MACHINE RECOVERY: This facility attempts to
resume execution of the preferred virtual machine after the VM/XA
Migration Aid has terminated with an abend and initiated an
SYSTEM PROGRAMMER TEST FACILITIES
VIRTUAL DYADIC: The Virtual Multiprocessor facility will provide
functional simulation of a System/370 Extended Architecture
multiprocessing computing system. The virtual MP facility is
provided through extensions to virtual machine definition,
dispatching, and command processing. Console commands are
provided to create and destroy, stop, start and query virtual
Note: Virtual dyadic will only be supported for extended
architecture virtual machines.
VIRTUAL MACHINE DEBUGGING: The debugging facilities of VM/XA
Migration Aid will provide a significant tool to aid in debugging
a virtual machine or virtual MP in the extended architecture
environment. For example:
o A BEGIN command starts execution of the virtual machines
processor (or the virtual architecture MP)
To look at a virtual machine's storage, the DISPLAY facility
displays storage at the user's terminal, and the DUMP
facility prints storage to the user's virtual printer.
o A STORE command can be used to alter storage and certain
architected areas of the virtual machine (such as general
registers, control registers, and PSW).
TRACE FACILITY: The trace function provides the ability to trace
the following events in a virtual machine:
o Any activity against an I/O device or against a range of
o Any storage alteration or alteration within a range of
storage. A value may be specified such that the event traced
is signaled when that value is set.
o Any general register alteration may be traced with an
optional value to be set.
o Selected mnemonics and special instructions can be traced.
VM/XA MIGRATION AID DEVICE SUPPORT LIST
2305 MOD 2
3330 MOD 1,11
3333 MOD 1,11
3350 MOD A2,B2,C2
3380 DEDICATED ONLY
3850 DEDICATED ONLY
Supported DASD Control Unit:
2835 MOD 2
3830 MOD 2,3
3851 DEDICATED ONLY
3880 MOD 1
3880 MOD 2,3 DEDICATED ONLY
3880 MOD 11,13 DEDICATED ONLY
3420 MOD 3,4,5,6,7,8
Tape Control Unit Supported:
1403 MOD 2,3,5,N1
3211 MOD 1
3800 DEDICATED ONLY
3525 MOD P1,P2,P3
3505 MOD B1,B2
2540 MOD 1
2501 MOD B1,B2
Unit Record Control Unit Supported:
Display Printers Supported:
(Key operator initiated copy only)
3287 MOD 1,1C,2,2C
3289 MOD 1,2
3277 MOD 2
3278 MOD 2,3,4
3279 MOD 2A,2B,3A,3B (4 COLOR ONLY)
Terminal Control Unit Supported:
3274 MOD 1B,1D
3274 MOD 21B,21D,31D
3272 MOD 2
Transmission Control Unit Supported:
3704 DEDICATED ONLY
3705 DEDICATED ONLY
CTCA DEDICATED ONLY
ALTERNATE PATH SUPPORT: The control required for alternate path
management is provided by the extended architecture channels.
DEDICATED DEVICES: Dedicated devices can be accessed through
multiple paths by the System/370-XA virtual machine if there are
multiple paths to the real device. Minidisks and simulated
devices however will be accessible only through the first path.
The Channel Path Identifiers will be the same for the dedicated
device as for the real device which supports it.
Note: Support for 3340 and 3344 alternate tracks is only
provided in dedicated mode by the virtual machine.
SPECIFIED OPERATING ENVIRONMENT
PROGRAMMING REQUIREMENTS: Assembler H Version 2 Release 1
(5668-962) is required for system generation of the VM/XA
Migration Aid and for the service of this product.
PROGRAM INTERFACES: The VM/XA Migration Aid will support only
the following systems:
MVS System Product V1 (JES2 or JES3) in a preferred area in UP
MVS System Product V1 (JES2 or JES3) in a V=V area in UP mode.
MVS/XA in a V=V area in UP and virtual MP mode.
VM/XA Migration Aid in a V=V area in UP and Virtual MP mode.
CMS/370 in a V=V area.
Note: MVS System Product means either MVS/SP 1 enhancement or
release 3 and later releases.
MACHINE REQUIREMENTS: The VM/XA Migration Aid is designed to run
on the IBM 3081 Processor complex modules D16, D24, D32, K16, K24
and K32 in the extended architecture mode only.
STORAGE ESTIMATES: The resident nucleus for the VM/XA Migration
Aid will be approximately 1M, and the minimum supported storage
size will be 4M.
The VM/XA Migration Aid will be shipped with the combined
1. VM/XA Migration Aid Control Program
2. VM/System Product CMS
While the VM/XA Migration Aid is a Virtual Machine Facility, its
functions will not be equivalent to any of IBM's VM/370 Products.
For example, VM/XA Migration Aid does not support:
1. The following devices (except when used in a dedicated mode
by an MVS Virtual Machine)
2. Networking facilities
3. Program Products
4. Remote terminals
5. Monitoring facilities
6. CMS use other than for installation and service of the VM/XA
Migration Aid, and migration from MVS/SP to MVS/XA.
The VM/XA Migration Aid user is a MVS customer who is ready to
migrate to MVS/XA and would like to continue MVS/SP non critical
work while testing MVS/XA and associated subsystems. MVS/SP will
be run as the preferred virtual machine on one processor of the
complex, and cannot be run in virtual MP mode. The MVS/XA test
virtual machines and CMS activity will run on the other processor
of the complex.
o VM/XA Migration Aid General Information Manual (GC19-6213),
will be available June, 1982.
Additional publications will be available at general
Central Service, including the IBM Support Center, will be
available until discontinued by IBM upon twelve (12) months
Local Licensed Program Support will be available until
discontinued by IBM upon twelve (12) months written notice.
Local Licensed Program Support will be provided under the terms
and conditions of the Agreement for Local Licensed Program
Support for IBM Licensed Programs at the Monthly Licensed Program
Support Charge, Monthly Additional Licensed Program Support
Charge, or will be provided at the applicable hourly rate. Local
Licensed Program Support will be provided by IBM Customer
TESTING PERIOD: 60 days.
WARRANTED: Yes, in accordance with the Agreement for IBM
INSTALLATION LICENSE APPLIES: No. A separate license is
required for each designated machine on which the licensed
program materials will be used except as otherwise provided by
Initial License Charges: ................... )
Monthly Charges: ........................... ) Consult your
Monthly Licensed Program Support Charge: ... ) IBM
Monthly Additional Licensed Program ) Marketing
Support Charge: .......................... ) Representative
PLANNED AVAILABILITY: By January 1984.