Availability Guide for Application Design

Data Protection and Recovery
Availability Guide for Application Design—525637-004
4-16
Remote Duplicate Transactions
Finally, you need to switch back to running the application on the original primary
system. This step does require taking the application offline for several minutes, but it
can be scheduled for the most convenient time.
For operational details on the RDF products, refer to the NonStop RDF System
Management Manual.
Figure 4-4. Remote, Duplicate Transactions Provide Protection Against Site
Failure
New
York
$DBNY
$AUDIT
Read Inbound Packet
Begin Transaction
Write to Database in New York
Write to Database in Chicago
Send Status to Chicago
Switch
End Transaction
Write Outbound Packet
Chicago
$DBNY
$AUDIT
Normal
Information
Flow
Flow When
Primary
Switch Down
Server Server
SwitchSwitch
Network
VST304.vdd