HP Reliable Transaction Router - Manual (Page 32)

RTR Server Types
Transactional shadowing is done by partition. A transactional
shadow configuration can have only two members of the shadow
set.
Shadow servers are servers on separate backends that handle
the same transactions in parallel on identical copies of the
database.
Figure 1–15 shows a simple shadow configuration. The main
backend server application at Site 1 and the shadow server
(Shadow application) at Site 2 both receive every transaction
for the data partition they are servicing. Should Site 1 fail,
Site 2 continues to operate without interruption. Sites can
be geographically remote, for example, available at separate
locations in a wide area network (WAN).
Figure 1–15 Shadow Servers
VM-0834A-AI
TR
FE
Terminals Frontends Router Backends Database
BE
Server
application
BE
Shadow
application
Client
application
FE
Client
application
FE
Client
application
Site 1
Site 2
1–20 Introduction