IBM DS8880 Series, Introduction And Planning Manual

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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 run 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) allows hosts, which are attached through a
FICON interface, to access data on fixed block (FB) volumes through a device
address on FICON interfaces.
If the zDDB LIC feature key is installed and enabled and a volume group type
specifies either FICON 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 IBM Z host. The feature helps
you manage multiple data protection environments and consolidate those into one
environment that is managed by IBM Z. For more information, see “z/OS
Distributed Data Backup” on page 122.
z/HPF extended distance
z/HPF extended distance reduces the impact that is associated with supported
commands on current adapter hardware, improving FICON throughput on the I/O
ports. The storage system also supports the new zHPF I/O commands for
multitrack I/O operations.
zHyperLink
zHyperLink is a short distance link technology that is designed for up to 10 times
lower latency than zHPF. It can speed up transaction processing and improve
active log throughput. zHyperLink is intended to complement FICON technology
to accelerate I/O requests that are typically used for transaction processing.
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 storage system 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 adapters, and a newer release of the
DS8000 (Release 6.0 or later), which supports 8-port host adapters, the paths
connect only to the lower four ports on the newer storage system.
v The maximum number of FlashCopy relationships that are allowed on a volume
is 65534. If that number is exceeded, the FlashCopy operation fails.
Chapter 3. Data management features
67