Section 6. Changes to VM/370 Restrictions A virtual machine created by V!/370 is capable of running 1n an System/360 er System/370 operating system with certain Vft/370 restrictions. The complete list of virtual machine restrictions and
certain execution characteristics are contained in GC2o-1808, and in !!L37Q GC20-1801. Significant changes to the V8/370 restrictions are defined in this
section. Dynamically Modified Channel Programs
No changes frem the previous release.
Minidisk Restrictions
No changes from the previous release.
Timing Dependencies
No changes from the previous release.
Processor Model Dependent Functions No changes frem the previous release. Channel Model Dependent Functions
No changes from the previous release. Virtual Machine Characteristics
No changes from the previous release. eMS Restrictions
No changes from the previous release. Section 6. Changes to V8/370 Restrictions 6-1

MSS Restrictions
1. There are two OS/VS system data sets associated with the 3850 Mass Storage System: a. The mass storage volume inventory
b. The mass storage volume control journal
There is only one copy of each data set per Mass Storage System, not
necessarily one per operating system. If more than one OS/VS system (running in either native mode or in a virtual machine) is connected
to a commcn Mass Storage System, then the OS/VS systems must share a common inventory and journal.
2. When a real 3330V device is dedicated to a virtual machine as a
virtual 3330V, the programming support in the virtual machine must recognize and access the virtual device as a 3330V. 3. The following must be compatible:
a. The definition of 3330V addresses in the MSC table b. The DMKRIO module
c. The IOGEN for any OS/VS system running in a virtual machine with
a dedicated MSC port.
The reason for maintaining compatibility and the way to ensure it is
explained in VMilIQ Gu!de, GC20-1807. 4. Each active volume in the "SS must have a unique volume nuater. If
the user wishes to have two or more user volumes having the same
volume serial (such as different versions of an OS/VS2 system residence vclume both having a volume serial of VS2037), then he must create two MSS volumes having different volume serials and
allocate the user volumes as ainidisks.
5. Mass Storage System volumes may not be used for VM/370 residence,
paging, sFooling, or temporary disk space.
6. The user must not change the volume of a real 3330V volume (the
volume serial as known by the MSC) except by using the OS/VS access method services utilities. If, for example, cylinder 0 of a 3330V is dedicated to a virtual machine, and that virtual machine alters
the volume serial using DDR, then the volume cannot be mounted. Miscellaneous Restrictions
The following new restrictions have been added:
1. VM/370 System Extensions Program Product Release 1 Modification
Level 0 and Release 1 Modification Level 1 as well as VM/310 Basic System Extensions Program Product Release 1 aFplicab1e to Release 5
do not function on Release 6.
However, VM/310 System Extensions Program Product Release 2 and VM/310 Basic System Extensions Program Product Release 2 function on
Release 6 but not on Release 5. These release levels contain all
the function of V8/370 Extensions applicable to Release 5 as well as
new function for Release 6.
6-2 IBM VM/370 Release 6 Guide