HP XP Continuous Access Software - Manual (Page 26)

Continuous Access Journal data volumes are quickly synchronized between DC2 and DC3 and
made available for use.
The delta resync operation consists of:
•
Preparation before the failure occurs (see Journal obtain in XPContinuous Access Synchronous
secondary sites )
•
Recovery after the failure occurs (see Switching XP'sContinuous Accessmaster journal group )
Journal obtain in XP Continuous Access Synchronous secondary sites
To perform the DC2-to-DC3 delta resync operation when a DC1 failure occurs, you must first obtain
journal data in DC2 the XP Continuous Access Synchronous secondary site with a 3DC multi-target
configuration. To create an XP Continuous Access Journal pair for an eventual delta resync
operation, specify the DC2 XP Continuous Access Synchronous S-VOL in the XP Continuous Access
Synchronous secondary site as the primary data volume, and specify the DC3 data volume in the
XP Continuous Access Journal secondary site as the secondary data volume.
When creating the contingency XP Continuous Access Journal pair for use with a DC2-to-DC3
delta resync operation, differential data for data volumes in the XP Continuous Access Synchronous
primary and secondary sites is stored as MCU journal data in journal volumes in the DC2 XP
Continuous Access Synchronous secondary site.
Figure 7 (page 26) shows an example.
Figure 7 Delta resync contingency configuration in a 3DC multi-target topology (before a failure
occurs)
As shown in Figure 7 (page 26) , an XP Continuous Access Journal contingency pair created with
the delta resync option is defined as a pair, but no copy operation is performed (HOLD status).
No copy operations are performed until a failure occurs and a delta resync operation is needed.
There are several requirements to create an XP Continuous Access Journal pair for delta resync
operations, such as specifying an unused mirror unit ID. For information about requirements for
26 Overview of XP Continuous Access Journal