HP XP Racks - Manual (Page 93)

Figure 48 Overview of an inter-control unit logical path dedicated to Cnt Ac-J Z command devices
For details on how to create an inter-control unit logical paths dedicated to command devices, see
“Creating an inter-control unit logical path dedicated to the command device ” (page 138) .
Functions that support disaster recovery
This section describes the Business Continuity Manager functions that support disaster recovery
(such as the Reverse Resync function and Continuous Access Synchronous consistency preservation
function).
The Reverse Resync function
The Reverse Resync function is used to reverse the direction of copy operations (reverse the roles
of the P-VOL and S-VOL). Because the Reverse Resync function only copies the differences between
a P-VOL and an S-VOL, it shortens the time required for recovering the operation.
Implement the Reverse Resync function by using the YKSUSPND and YKRESYNC commands, in
combination.
The following procedure describes the flow of failovers and failbacks using the Reverse Resync
function. The numbers in the following steps correspond to the numbers in
Figure 49 (page 94) .
1. Stop all applications at the primary site.
2. Reverse the copy direction by using the Reverse Resync function.
To reverse the copy direction, execute the YKSUSPND and YKRESYNC commands with the
REVERSE
parameter specified for both.
3. Start all applications at the secondary site.
Perform a maintenance and failure recovery at the primary site while operations are being
performed at the secondary site.
4. Reverse the copy direction again using the Reverse Resync function.
To return the copy direction back to the original direction, execute the YKSUSPND and
YKRESYNC
command with the FORWARD parameter specified for both.
5. Start all applications at the primary site.
Functions that support disaster recovery 93