IBM eServer zSeries 990 Technical Guide

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