40
On the other hand, the GDPS solution based on Extended
Remote Copy (XRC), referred to as GDPS/XRC, has the
attributes of a Disaster Recovery solution. XRC is a com-
bined hardware and software asynchronous remote copy
solution. The application I/O is signaled completed when
the data update to the primary storage is completed. Sub-
sequently, a DFSMSdfp
™
component called System Data
Mover (SDM), typically running in site 2, is designed to
asynchronously offl oad data from the primary storage sub-
system’s cache and updates the secondary disk volumes.
In GDPS/XRC, the production system(s) located in site 1
can be a single system, multiple systems sharing disk, or
a base or Parallel Sysplex cluster. GDPS/XRC is designed
to provide a single, automated solution to dynamically
manage storage subsystem mirroring (disk and tape)
to allow a business to attain “near transparent” disaster
recovery with minimal data loss. GDPS/XRC is designed to
provide the ability to perform a controlled site switch for an
unplanned site outage, maintaining data integrity across
multiple volumes and storage subsystems GDPS/XRC is
designed to be application independent and therefore is
capable of covering the customer’s complete application
environment.
GDPS requires Tivoli
®
NetView
®
for z/OS or Tivoli NetView
for OS/390, Tivoli System Automation for OS/390, and
remote copy technologies.
Note: Dark fi ber refers to dedicated strands of fi ber optic
cable with no electronics between the ends (source and
destination).
Geographically Dispersed Parallel Sysplex HyperSwap
™
The GDPS/PPRC HyperSwap function is designed to
broaden the continuous availability attributes of GDPS/
PPRC by extending the Parallel Sysplex redundancy to
disk subsystems. The HyperSwap function can mask
planned and unplanned disk and site reconfi gurations
by transparently switching to use the secondary PPRC
volumes. The HyperSwap function is designed to be con-
trolled by complete automation, allowing all aspects of the
site switch to be controlled via GDPS.
The HyperSwap function planned provides the ability to
transparently switch all primary PPRC disk subsystems
with the secondary PPRC disk subsystems for a planned
switch confi guration. It enables disk confi guration mainte-
nance and planned site maintenance without requiring any
applications to be quiesced. Large confi gurations can be
supported, as HyperSwap has been designed to provide
capacity and capability to swap large numbers of disk
devices very quickly. The important ability to re-synchro-
nize incremental disk data changes, in both directions,
between primary/secondary PPRC disks is provided as
part of this function.
The unplanned HyperSwap function contains additional
function designed to transparently switch to use second-
ary PPRC disk subsystems, in the event of unplanned
outages of the primary PPRC disk subsystems or a failure
of the site containing the primary PPRC disk subsystems.
With unplanned HyperSwap function, disk subsystem
failures no longer constitute a single point of failure for
an entire sysplex. If applications are cloned and exploit-
ing data sharing across the two sites, the GDPS/PPRC
