Minidisks
In addition, all virtual machine minidisks should have a
virtual cylinder0, track 0, record 3. Labels created by IEHDASDR, or INTDK
label atIBCDASDI, VOL1xxxxxx where xxxxxx is a 6-character volume label.
A physical volume that holds only virtual machine minidisks can have
the first of those minidisks starting at real cylinderO. CP recognizes
the physical volume if the first minidisk has a valid label.
In Figure 16, the volume indicated asOSDOS1 has
allocated to a minidisk that is formatted for use
serial number of that minidisk must beOSDOS1, associated with the real volume. Since the minidisk
physical volume, changing it affects the directory
who have minidisks on that volume.
its real cylinder0 by os. The volume
the label that is
label identifies the
entries of all usersYou should not assign real cylinder
because that user (if he has read/write
the label on the minidisk.
o to a user as a data area,
access to the disk) can rewrite
Additionally, you must not assign user minidisks to begin on real
cylinder0 of any physical volumes that are to contain CP controlled
areas (for paging, spooling, and so on).On these volumes, cylinder 0 track 0 record 4 contains control information required by CP. The VTOC labels written are compatible with OS, but indicate to OS that there is
no space on thatDASD. The initialization programs used to format OS, DOS, and CMS/VSAM minidisks write over and destroy this necessary
control information if the space is assigned to a user minidisk, and
this causesCP system failures.
Sharing Minidisks
A minidisk can be shared by multiple virtual machines.One virtual
machine is designated the owner of the minidisk (it has anMDISK control
statement in itsVM/370 directory entry describing the minidisk) and
other virtual machines can link to the minidisk.
For example, assume a virtual machine calledUSERA owns a minidisk at
address150. The VM/370 directory entry for USER! contains the
following statement:MDISK 150 3330 050 010 SYS003 W READPASS USERA's virtual disk is on the volume labeled SYS003 and occupies real
cylinders050-059. Any other virtual machine that issues the CP LINK command with the
proper password, or has the following LINK statement in itsVM/370 directory entry, can read the 150 minidisk belonging to USER!. LINK USERA 150 cuu RR
The cuu is the virtual device address at which the150 minidisk
belonging toUSERA is linked to another virtual machine. If you define
another virtual machine,USERB, with the following statement in its VM/3?0 directory entry:
LINKUSERA 150 151 RR Part 1. Planning for System Generation 101
In addition, all virtual machine minidisks should have a
virtual cylinder
label at
A physical volume that holds only virtual machine minidisks can have
the first of those minidisks starting at real cylinder
the physical volume if the first minidisk has a valid label.
In Figure 16, the volume indicated as
allocated to a minidisk that is formatted for use
serial number of that minidisk must be
physical volume, changing it affects the directory
who have minidisks on that volume.
its real cylinder
the label that is
label identifies the
entries of all users
because that user (if he has read/write
the label on the minidisk.
o to a user as a data area,
access to the disk) can rewrite
Additionally, you must not assign user minidisks to begin on real
cylinder
areas (for paging, spooling, and so on).
no space on that
control information if the space is assigned to a user minidisk, and
this causes
Sharing Minidisks
A minidisk can be shared by multiple virtual machines.
machine is designated the owner of the minidisk (it has an
statement in its
other virtual machines can link to the minidisk.
For example, assume a virtual machine called
address
following statement:
cylinders
proper password, or has the following LINK statement in its
The cuu is the virtual device address at which the
belonging to
another virtual machine,
LINK