HP StorageWorks XP Remote Web Console Software - Manual (Page 84)

Update sequence consistency will be maintained with the Universal Replicator for Mainframe
secondary data volume.
In addition, you can create the Universal Replicator for Mainframe pair for the delta resync operation
in 3DC multi-target configuration by specifying, as the Universal Replicator for Mainframe primary
data volume, the TrueCopy for Mainframe Synchronous R-VOL in the TrueCopy for Mainframe
Synchronous secondary site, and by specifying the volume in the Universal Replicator for Mainframe
secondary site as the Universal Replicator for Mainframe secondary data volume. If you create the
Universal Replicator for Mainframe pair for the delta resync operation, you can resynchronize the
Universal Replicator for Mainframe pair using journal data in the TrueCopy for Mainframe
Synchronous secondary site when a failure occurs in the primary site.
If you want to perform the normal delta resync operation, a certain amount of data must be updated
on the TrueCopy for Mainframe Synchronous primary site. However, the delta resync operation
can be performed if only a small amount of data to be updated exists on the TrueCopy for
Mainframe Synchronous primary site. Therefore, even if a disaster occurs and only a small amount
of data exists, the delta resync operation can be performed. If you use the delta resync function
to resume business tasks from the disasters or failures, you must use the delta resync function to
support remote command devices.
For detailed information about the hardware configuration required for a 3DC multi-target
configuration, see the next section. For detailed information about the requirements to create a
Universal Replicator for Mainframe pair for the delta resync operation, see
“Requirements for
Creating Universal Replicator for Mainframe Pair for the Delta Resync Operation” (page 87) . As
for the requirements to perform the delta resync operation, see “Requirements for Performing a
Delta Resync Operation” (page 87) . For detailed information about the requirements to create the
delta resync operation environment to support remote command devices, see “Configuring Delta
Resync Operation Environment to Support Remote Command Devices” (page 88) .
If a failure occurs in a TrueCopy for Mainframe Synchronous primary volume, which is also used
as a Universal Replicator for Mainframe primary data volume, you can resume business tasks by
using the TrueCopy for Mainframe Synchronous secondary volume. After you resume the business
tasks, you need to remove the failure from the primary volume and transfer the business tasks back
to the primary site. For details, see
“Recovering from a Disaster at the Main Site in a 3DC
Multi-Target Configuration” (page 224) and “Changing to 3DC Multi-target Configuration after
Recovering from Primary Site Failures” (page 89) .
If a failure occurs in both the primary volume and the TrueCopy for Mainframe Synchronous
secondary volume, you can resume your business tasks by using the Universal Replicator for
Mainframe secondary data volume. After you resume the business tasks, you need to remove the
failure from the primary volume and the TrueCopy for Mainframe Synchronous secondary volume,
and transfer the business tasks back to the primary site. For details, see
“Recovering from Failures
in the Primary Site and the TrueCopy for Mainframe Synchronous Secondary Site” (page 95) and
“Transferring Business Tasks from the Universal Replicator for Mainframe Secondary Site to the
Primary Site” (page 96)
.
The response time for host I/Os is the sum of the response time for TrueCopy for Mainframe
Synchronous operation and the creation time of journal data in an intermediate site. As for the
delta resync configuration, the response time for host I/Os is the sum of the above mentioned time
and the creation time of journal data in the TrueCopy for Mainframe Synchronous S-VOL.
The utilization rate of the primary site in the 3DC multi-target configuration rises compared with
the configuration which consists of only TrueCopy for Mainframe Synchronous or Universal Replicator
for Mainframe. In addition, the utilization rate of the primary site in the 3DC multi-target
configuration rises compared with the configuration which consists of only data volumes.
If the CFW option that is specified to either the Universal Replicator for Mainframe or TrueCopy
for Mainframe Synchronous pair is defined as Copy to S-VOL, the cache-fast-write data is copied
to both secondary data volumes of Universal Replicator for Mainframe and TrueCopy for Mainframe
Synchronous pairs.
84 Preparing for Universal Replicator for Mainframe Operations