188 IBM eServer zSeries 900 Technical Guide
PPRC (Peer-to-Peer Remote Copy) architecture
XRC (Extended Remote Copy) architecture
Virtual Tape Server Remote Copy architecture
GDPS supports both the synchronous (PPRC) as well as the asynchronous (XRC) forms of
There is new Enhanced HMC support for GDPS/PPRC and GDPS/XRC configurations.
GDPS/PPRC and GDPS/XRC configurations are significantly enhanced in terms of
availability and simplified configuration. These enhancements are made available for GDPS
configurations by use of new operating system support, which is designed to eliminate the
need for a previously required workstation in the GDPS configuration, thus simplifying the
configuration. This support is available with IBM zSeries driver 3G and IBM G5/G6 driver 26,
with current maintenance levels, and z/OS V1.2 and later with the service defined in the PSP
Bucket for MSYSOPS.
GDPS/PPRC is a hardware solution that synchronously mirrors data residing on a set of disk
volumes, called primary volumes in the application site, to secondary disk volumes on the
second system at another site. Only when the application site storage subsystem receives
“write complete” from the recovery site storage subsystem is the I/O signaled as completed.
The physical topology of a GDPS/PPRC consists of a base or Parallel Sysplex cluster spread
across two sites (site A and site B) separated by up to 40 km (approximately 25 miles), with
one or more z/OS and/or OS/390 systems at each site; see Figure 5-5 on page 189. The
multisite Parallel Sysplex cluster must be configured with redundant hardware (for example, a
Coupling Facility and a Sysplex Timer in each site), and the cross-site connections must be
All critical data resides on storage subsystems in site A (the primary copy of data) and is
mirrored to site B (the secondary copy of data) via PPRC synchronous remote copy.
The new 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 GDPS/PPRC hyperswap function provides the ability to transparently switch all primary
PPRC disk subsystems with the secondary PPRC disk subsystems for a planned switch
reconfiguration. Planned for release in the second half of 2002, it is designed to provide the
ability to perform disk configuration maintenance and planned site maintenance without
requiring any applications to be quiesced.
GDPS/PPRC provides the following benefits:
Near transparent disaster recovery
Recovery Time Objective (RTO) less than an hour (will be a minute with hyperswap).
Recovery Point Objective (RPO) of zero (optional)
Protects against metropolitan area disasters
GDPS/PPRC hardware requirements
GDPS/PPRC requires the following hardware configuration:
The multisite Parallel Sysplex cluster must be configured with redundant hardware across
Chapter 5. Sysplex functions 189
The systems in a Parallel Sysplex cluster must have full connectivity (CTC connectivity, CF
XCF connectivity, or both) for Parallel Sysplex cluster communication.
The systems must be attached to a Sysplex Timer (IBM 9037 Model 2) in the expanded
Primary couple data sets—including the Parallel Sysplex cluster, automatic restart
manager (ARM), coupling facility resource management (CFRM), system logger (LOGR),
Parallel Sysplex cluster failure manager (SFM), and workload manager (WLM)—must
reside at site A and the alternate couple data sets reside at site B.
Each system must have its own set of disks for system-related data sets/volumes (such as
system residency volume, master catalog, paging volumes, LOGREC data sets, and SMF
data sets) because each site must be able to function if access is lost to the storage
subsystems in the other site.
Storage subsystem with PPRC level 2 (includes the Freeze function) is required.
GDPS/PPRC software requirements
GDPS/PPRC requires the following software:
z/OS Version 1 Release 1 or higher
Tivoli Netview for OS/390 Version 1 Release 2 or higher
System Automation for OS/390 Version 1 Release 2 or higher
Figure 5-5 GDPS/PPRC
With GDPS/PPRC hyperswap function, the speed of GDPS site reconfigurations can be
significantly improved. Stage 1 of the hyperswap function, available with GDPS 2.7 in the
second half of 2002, provides the ability to transparently switch all primary PPRC disk
subsystems with the secondary PPRC disk subsystems for a planned switch reconfiguration.
40km max with
IBM Fiber Saver