IBM 990 - Manual (Page 189)

Chapter 7. Sysplex functions 177
The physical topology of a GDPS/XRC, shown on Figure 7-11, consists of a production site
(Site 1) and a recovery site (Site 2) located virtually at any distance from Site 1.
Figure 7-11 GDPS/XRC
GDPS/XRC is capable of the following attributes:
Disaster recovery
RTO between one and two hours
RPO less than two minutes
Protects against metropolitan as well as regional disasters (distance between sites is
unlimited)
Minimal remote copy performance impact
In a GDPS/XRC configuration, it is often necessary to have multiple System Data Movers
(SDMs). The number of SDMs is based on many factors, such as the number of volumes
being copied, the I/O rate, and so on. Functions are now capable of being executed in parallel
across multiple SDMs, thus providing improved scalability for a coupled SDM configuration.
7.4.3 GDPS and Capacity Backup (CBU)
GDPS consists of production images and controlling images. The production images execute
the mission-critical workload. There must be sufficient processing resource capacity, such as
processor capacity, main storage, and channel paths available, that can quickly be brought
online to restart an image's or site's critical workload. Typically, this is accomplished by
terminating one or more systems executing expendable (non-critical) work and acquiring their
processing resource.
The Capacity Backup (CBU) feature, available on the zSeries, provides a significant cost
savings. The CBU feature has the ability to increment capacity temporarily, when capacity is
lost elsewhere in the enterprise. CBU adds Central Processors (CPs) to the available pool of
processors and is activated only in an emergency.
Channel
Extenders
CE
CE
CE
CE
Site 1
Application
Systems
Application
Systems
Site 2
Secondary
volumes
and SDM
Control Data sets
Primary
volumes
SW SW
Recovery
Systems
SDM System
Data mover
CF01
1 2
3
4
5 6 7
8
9
10
11 12