HP XP Continuous Access Software - Manual (Page 27)

When journal data S2 arrives, the secondary storage system selects S2 as the next journal data
to be settled. The journal data selected by the secondary storage system is marked as host-dirty
and treated as formal data.
Figure 6 Selecting and Settling Journals at the Secondary Storage System
The secondary storage system settles and restores the journal data to the secondary data volume
as follows:
•
Journal data stored in the cache
The journal data is copied to the corresponding cached track and promoted to formal data.
•
Journal data stored in the restore journal volume
The journal data is read from the restore journal volume to cache. The journal data that is
read to cache is copied to the existing cache track and promoted to formal data. After that,
the space for the restore journal volume is released.
XP Continuous Access Journal Delta Resync Operation
When using XP Continuous Access Journal and XP Continuous Access Synchronous in a 3DC
multi-target configuration, XP Continuous Access Journal provides the delta resync operation as a
way to recover from failures in the primary site. In a 3DC multi-target configuration, there is one
primary site and two secondary sites. XP Continuous Access Journal is primary; XP Continuous
Access Synchronous and XP Continuous Access Journal provide the secondary sites. For detailed
information about the 3DC multi-target configuration, see
“XP Continuous Access Synchronous
(3DC Cascading Configuration)” (page 82) .
If a failure occurs on the primary site in the 3DC multi-target configuration, use the RAID Manager
horctakeover
command to reconfigure the XP Continuous Access Synchronous secondary site
as the primary site. Perform the delta resync operation after the XP Continuous Access Synchronous
secondary site becomes a primary site. The XP Continuous Access Journal pair is restored quickly
XP Continuous Access Journal Delta Resync Operation 27