Software Manual

*4: HOLDING indicates that the differential data to be used for a delta resync operation either
does not exist in the storage system, or either the storage system cannot determine whether the
delta resync operation can be performed without the differential data to be used for a delta resync
operation. When the differential data to be used for a delta resync operation does not exist in the
XP Continuous Access secondary site of even if you update the data from the host on the primary
site, the differential data might have been discarded due to the following conditions:
• The cache or shared memory was added to or reduced from the storage system during the
maintenance work.
• The storage system was powered off during the maintenance work.
• The XP Continuous Access Journal Software pair or XP Continuous Access pair was suspended,
and then the pair has been resynchronized.
• The journal volume could not be accessed because a disaster or failure occurred in the
secondary site of XP Continuous Access.
After each problem is recovered, the differential data are stored in the XP Continuous Access
secondary site.
The state in which the delta resync operation can be executed without the differential data for the
delta resync is when the data update to the primary site is not executed or both the data of the XP
Continuous Access secondary site and the XP Continuous Access Journal secondary site are
coincident. To create the above mentioned condition, cause the configuration that executes the
delta resync operation in question to utilize remote command devices and then change the status
of all XP Continuous Access Journal pairs and XP Continuous Access pairs which belong to the
desired journal group in the primary site to PAIR by the resynchronizing operation.
Even if the delta resync operation without the differential data is executable, the pair status will
change to HOLD. This status occurs regardless of whether the differential data that exists if the
conditions of the discarded differential data are satisfied. To change the status of the pair to HOLD,
update the data in the primary disk system after recovering from discarding the differential data.
If you cannot connect to the XP Continuous Access secondary site due to failure or disaster, the
transition from HOLDING to HOLD will not be performed correctly.
Split Types (PSUS)
Table 6 (page 39) lists and describes the XP Continuous Access Journal split types.
• A user can split an XP Continuous Access Journal pair at any time after the initial copy operation
is complete.
• The user must split an XP Continuous Access Journal pair in order to perform media maintenance
on the primary data volume or to access the secondary data volume (secondary data volume
write enable).
Split Pair – Synchronization: When an XP Continuous Access Journal pair is split by the user, the
primary storage system and secondary storage system ensure synchronization by either completing
or discarding any pending update copy operations according to the user-specified pending update
option (purge/flush).
Tracking Journal Data: The primary storage system and secondary storage system keep track of
any journal data that was discarded during the pairsplit operation. After the pair status changes
to PSUS, the primary storage system performs the following tasks:
• Stops performing journal obtaining operations for the pair
• Continues accepting write I/Os for the split XP Continuous Access Journal primary data volume
• Keeps track of the primary data volume tracks which are updated while the pair status is split
If you enabled the secondary data volume write option when you split the pair, the secondary
storage system keeps track of the secondary data volume tracks that are updated while the pair
is split.
38 About XP Continuous Access Journal Operations