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

2. When using the SPOOL, DEDICATE, and SPECIAL directory control
statements to define virtual devices, the user must specify virtual
addresses that do not conflict or contend with the virtual centrol
unit interface. This conflict or contention occurs tecause devices
can require special I/O interface protocol from control units such
as shared and nonshared sunchannel operations. Putting devices that
require different read control units on the same virtual centrol
unit can result in a hung or busy condition. 10 avoid this problem,
the user must define (and separate) devices within their own centrol
unit range. For example, if the directory entries specify: SPOOL 102 3211 SPECIAL 103 3270 the control unit 0 on channel 1 controls both a nonshared device
(the 3211 printer) and a shared device (the 3270 display unit).
Processing of channel programs involving these two devices can
result in a hung or busy condition. Section 64 Changes to V!j370 Restrictions 6-3