HP XP Racks - Manual (Page 31)

Figure 6 Overview of arbitration processing in an extended consistency group
A supervisor DKC checks the timestamps of update journal data that has been sent to the restore
journals for all the consistency groups in an extended consistency group. A timestamp is a record
of the time data was written to a P-VOL from a host. All the update journal data up to the time of
the oldest timestamp (10:00:02) among the most recent update journal data for every consistency
group (URG01: 10:00:03; URG02: 10:00:02; URG03: 10:00:04) is reflected onto the S-VOL.
The following command devices are used in the execution of arbitration processing:
•
Arbitration command device: A command device defined in a subordinate DKC for
communicating between the supervisor DKC and the subordinate DKC.
•
Remote command device: An arbitration command device in a subordinate DKC mapped to
the supervisor DKC as an external volume for communicating between the supervisor DKC
and the subordinate DKC.
The method for checking whether consistency is preserved for an EXCTG is the same as that for a
consistency group. For details, see
“How to check whether consistency is preserved” (page 27) in
“Consistency groups” (page 25) . To make sure that the consistency of an EXCTG is preserved, the
EXCTG must be properly registered in the storage system. You can verify whether an EXCTG is
properly registered in a storage system by making sure that the YKQUERY command ends normally.
Grouping to simplify volume operations 31