HP XP Continuous Access Software - Manual (Page 25)

Journal types
In addition to sending journal data for updating, the primary array sends control information to
the secondary array. This control information:
•
Indicates volume pair status changes.
•
Indicates when a primary array power-off sequence is has been initiated.
•
Maintains sequence numbers in periods of low host activities.
Journal group operations
Journal groups maintain update sequence consistency across a group of journal volumes. The
primary and secondary data volumes of the pairs in a journal group must be located logically
within one physical primary array and one physical secondary array (1-to-1 requirement).
When more than one data volume is updated, the order in which data volumes are updated is
managed within the journal group to which the data volumes belong. Data update consistency is
maintained among paired journal groups. XP Continuous Access Journal uses journal groups to
maintain data consistency among data volumes.
XP Continuous Access Journal provides the following group-based operations to simplify and
expedite disaster or failure recovery procedures:
•
Group operations at the primary array
Split all pairs in a journal group. See Splitting mirrors (Pairsplit-r: suspending copy
operations) for a description of the Suspend Range-Group pairsplit option.
◦
◦ Resume all suspended pairs in a journal group. See Restoring mirrors (Pairresync: resuming
copy operations) for a description of the Resume Range-Group pairresync option.
◦ Delete all pairs in a journal group. See Deleting data volumes from mirrors (Pairsplit-S:
ending copy operations) for a description of the Delete Range-Group pairdelete option.
•
Group operations at the secondary array
Split (pairsplit-r) all pairs in a journal group. See Splitting mirrors (Pairsplit-r: suspending
copy operations) for a description of the Suspend Range-Group pairsplit-r option.
◦
◦ Delete (pairsplit-S) all pairs in a journal group regardless of their consistency status. See
Deleting data volumes from mirrors (Pairsplit-S: ending copy operations) for a description
of the Delete Range-Group pairsplit-S option.
XP Continuous Access Journal delta resync operations
When using XP Continuous Access Journal and XP Continuous Access Synchronous in a 3DC
multi-target configuration, XP Continuous Access Journal provides a delta resync operation between
the two original secondary sites as one of the solutions for failures in the primary site. In a 3DC
multi-target configuration, there is one primary site (DC1) and two secondary sites; XP Continuous
Access Synchronous (DC2) and XP Continuous Access Journal secondary sites (DC3). A dormant
DC2-to-DC3 XP Continuous Access Journal logical connection will only be invoked if DC1 becomes
disabled. Under those circumstances, it is desirable to uses a delta-update as opposed to a full
copy in order to bring DC2 and DC3 into synchronization. For more information, see
Combining
Continuous Access XP Journal with Continuous Access XP Synchronous (3DC multi-target
configuration)
.
If a failure occurs on the primary site in a 3DC multi-target configuration, you must first use the XP
RAID Manager horctakeover command to begin using the XP Continuous Access Synchronous
secondary site (DC2) as the new primary site. If you perform a delta resync operation (between
the two previous secondary sites; DC2 and DC3) after the XP Continuous Access Synchronous
secondary (DC2) site becomes the primary site, a delta resync operation is able to quickly activate
and synchnonize the previously dormant DC2-to-DC3 XP Continuous Access Journal pair. XP
Journal group operations 25