HP XP Continuous Access Software - Manual (Page 81)

NOTE:
Right after you create the Continuous Access XP Journal pair for delta resync operations or if a
failure occurs at the primary site right after the recovery of a Continuous Access XP Synchronous
or Continuous Access XP Journal pair, only part of the differential data between the primary and
secondary data volume might be stored in the master journal group.
When any of these requirements is not fulfilled, an error usually occurs and delta resync operations fail.
Especially in the following cases, delta resync operations are not performed because the necessary
journal data does not exist:
• When the primary data volume in the Continuous Access XP Journal pair for delta resync
operation is updated after creating the Continuous Access XP Journal pair, but Continuous Access
XP Journal primary data volumes that are also used as Continuous Access XP Synchronous
primary data volumes are not updated in the primary site
• When volumes in the primary site are not updated after creating the Continuous Access XP
Journal pair for delta resync operations (the journal does not yet contain any data)
• When volumes in the primary site are updated after splitting a Continuous Access XP Synchronous
pair (S-vol out of date)
• When the secondary data volume is updated after splitting a Continuous Access XP Journal pair
(S-vol data is newer than P-vol data).
• As a result of the update of the primary data volume after splitting Continuous Access XP Journal
pair, when the capacity of the journal data exceeds 70% of the journal volume in Continuous
Access XP Synchronous secondary site
• When the primary data volume in the UR pair for delta resync operation is updated and then the
capacity of the journal data exceeds 70% of the journal volume in the primary site of UR pair
for delta resync operation
• When no volumes (including volumes after failover or failback) in the primary site are updated
after creating the Continuous Access XP Journal pair for delta resync operation (the original
P-vol data is newer than the delta update P-vol)
• When delta resync operation is performed within about one minute after a volume in the primary
site is updated after the Continuous Access XP Journal pair for delta resync operation is created
By specifying a particular option, you can copy data items in the primary volume to the secondary
volume and avoid the error when only part of the differential data between primary and secondary data
volume is stored in the journal volume. For more information, see Changing options for journal groups .
Recovering from primary site failures (prior to 50-08-xx firmware)
If a disaster or failure occurs only at the primary site in a 3DC multi-target system, use the secondary
volume at the Continuous Access XP Synchronous secondary site to enable the secondary site to take over
your business tasks. After transferring your business tasks to the secondary site, remove the failure from
the primary site, so you can transfer your business tasks back to the primary site.
To transfer your business tasks to the Continuous Access XP Synchronous secondary site:
1. Use RAID Manager XP to delete the Continuous Access XP Journal pair.
2. Use RAID Manager XP to execute the horctakeover command on the Continuous Access XP
Synchronous pair.
3. Use the Continuous Access XP Synchronous secondary volume to resume your business tasks.
4. Check the execution results of the horctakeover command, and do either of the following:
a. If the Continuous Access XP Synchronous pair's primary/secondary relationship is not reversed
(that is, the copy direction is not reversed as illustrated in the upper-right portion of Figure 32 (
because the primary site is no longer operational), use RAID Manager XP to create a new (full
copy) Continuous Access XP Journal pair. The Continuous Access XP Journal pair's primary
data volume must be the Continuous Access XP Synchronous secondary volume. The Continuous
Continuous Access XP Journal user guide 81