its operation. These units connect to the Mass Storage Facility and to
the processor through a Staging Adapter. The several models of the
one of the following:
1. Real
2. Staging
3. Convertible
Real
activity. They are physically part of the system in that they have a
data and control path through a Staging Adapter, but real drives are not
logically connected to the
to hold data staged from mass storage volumes to be available for
processing by the processor. Staging packs are divided into pages of
storage. Each page consists of eight cylinders. The term virtual
volume is used to refer to pages of space and the data staged to that
space. Each virtual volume is assigned a virtual unit address. Staging
only one staging drive group. There can be no more than two staging
drive groups for each Staging Adapter. Each staging drive group can
have a maximum of eight logical $taging drives, a logical drive being
the equivalent of one
logical staging drives.
Convertible drives can be either real or staging drives, but not both
at the same time. If the drive is to be made real, the real path
between the drive and the operating system must be available.
drive is a staging drive, this real path must be offline.
most four channel interfaces to a single processor and the
Staging Adapter can have a maximum of four channel interfaces. The
first channel interface on the
control unit position of the 3851
not conflict with the previously mentioned
remaining three channel interfaces of the
more host systems.
generated should be defined as primary or alternate channels.
For each of the three rema1n1ng (available) channel interface
Thus, for each
with the Staging Adapter feature, there are 192 possible device
addresses. Each device address corresponds to pages of staging space on
the staging
allocated by the
and the
to the host processor, the staging space allocated to the device, and
the
channel interface
supported in
to access the
dedicated to the virtual machine.
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