Copy Services - IBM DS8800 Introduction And Planning Manual

to different domains. (The domain of an I/O operation is the specified extents to
which the I/O operation applies.)
Multiple allegiance
With multiple allegiance, the storage unit can execute concurrent, multiple requests
from multiple hosts.
Traditionally, IBM storage subsystems allow only one channel program to be active
to a disk volume at a time. This means that, once the subsystem accepts an I/O
request for a particular unit address, this unit address appears "busy" to
subsequent I/O requests. This single allegiance capability ensures that additional
requesting channel programs cannot alter data that is already being accessed.
By contrast, the storage unit is capable of multiple allegiance (or the concurrent
execution of multiple requests from multiple hosts). That is, the storage unit can
queue and concurrently execute multiple requests for the same unit address, if no
extent conflict occurs. A conflict refers to either the inclusion of a Reserve request
by a channel program or a Write request to an extent that is in use.
z/OS Distributed Data Backup
z/OS Distributed Data Backup (zDDB) is an optional licensed feature that allows
hosts, attached through a FICON or ESCON interface, to access data on fixed block
(FB) volumes through a device address on FICON or ESCON interfaces.
If the zDDB LIC feature key is installed and enabled and a volume group type
specifies either FICON or ESCON interfaces, this volume group has implicit access
to all FB logical volumes that are configured in addition to all CKD volumes
specified in the volume group. In addition, this optional feature enables data
backup of open systems from distributed server platforms through a System z
host. The feature helps you manage multiple data protection environments and
consolidate those into one environment managed by System z. For more
information, see "z/OS Distributed Data Backup" on page 135.
z/HPF extended distance
z/HPF extended distance reduces the impact associated with supported commands
on current adapter hardware, improving FICON throughput on the DS8000 I/O
ports. The DS8000 also supports the new zHPF I/O commands for multitrack I/O
operations.

Copy Services

Copy Services functions can help you implement storage solutions to keep your
business running 24 hours a day, 7 days a week. Copy Services include a set of
disaster recovery, data migration, and data duplication functions.
The DS8000 series supports Copy Service functions that contribute to the
protection of your data. These functions are also supported on the IBM
TotalStorage Enterprise Storage Server.
Notes:
v If you are creating paths between an older release of the DS8000 (Release
5.1 or earlier), which supports only 4-port host adaptors, and a newer
55
Chapter 3. Data management features