HP StorageWorks P9000 User Manual page 34

Figure 4 Using Continuous Access Journal Z with multiple storage systems
When primary hosts write data to P-VOLs, the hosts add a time stamp to the data. Secondary
systems check time stamps and then restore data to data volumes in chronological order (older
data are restored earlier), so that data update sequence is maintained. For details on the time
stamping function, see
The term "arbitration processing" refers to the maintenance of the data update sequence through
the execution of the journal restore function based on time stamps. When there is more than one
secondary system, one of them is used to perform tasks, including arbitration processing, on the
other secondary systems. The secondary system that performs arbitration processing is called the
"supervisor DKC." Systems that are controlled by the supervisor DKC and are targets of arbitration
processing are called "subordinate DKCs."
The supervisor DKC compares time stamps of data received by all the secondary systems (including
the local system) and then performs arbitration processing.
The supervisor DKC must be connected with the subordinate DKCs. For details on connections
between secondary systems, see
Please note the following when working with multiple systems:
Remote Web Console computers must be installed at primary and secondary sites.
BCM should be installed on the host in both the primary and secondary sites.
A remote command device must be created in the supervisor DKC. For details on secondary
systems connections and remote command devices, see the next section and HP StorageWorks
P9000 External Storage for Open and Mainframe Systems User Guide.
Journal data is updated in the secondary systems based on the same time stamps and sequence
numbers issued by the host when the host issues the write requests to the primary system(s).
Time and sequence information remains with the data as it moves to the master and restore
journals and then to the secondary volume.
34 Planning volumes, systems
"Host I/O time stamp" (page
Figure 4 (page
28).
34).