HP StorageWorks XP Remote Web Console Software - Manual (Page 64)

1. The primary host issues write requests to primary storage systems. Time stamps are added to
the data to be written.
2. The primary storage systems receive the write requests, and then notify the primary host that
primary data volumes are updated.
3. The Universal Replicator for Mainframe journal obtain function stores data updated in primary
data volumes to master journal volumes as journal data. Time stamp information added by
the primary host will be added to the journal data. Also, sequence numbers indicating the
order of writing will be added to the journal data.
4. The Universal Replicator for Mainframe journal copy function copies journal data from the
master journal volumes to the corresponding restore journal volumes. This journal copy
operation will be performed asynchronously with the journal obtain operation.
5. Secondary storage system 1 (that is, the supervisor DKC) performs arbitration processing. In
other words, secondary storage system 1 restores the journal data of secondary storage
systems 1 and 2, based on the time stamps and the sequence numbers added to the journal
data, so that consistency with the primary data volume is maintained.
The flow of the arbitration processing is as follows:
1. From journal data in restore journal groups registered in the extended consistency group, the
supervisor DKC collects the time stamps of journal data that has not been restored.
2. The supervisor DKC compares the time stamps, and then selects the oldest time stamp.
3. The supervisor DKC requests the subordinate DKCs to restore the journal data that has the
selected time stamp.
4. From journal data having the time stamp and earlier time stamps, the subordinate DKCs restore
all journal data that has not been restored, in the order of the sequence numbers.
Hardware Configuration for Multiple Primary and Secondary Storage Systems
This section explains the hardware configuration when more than one primary and secondary
storage system are used.
It is recommended that Business Continuity Manager is installed on the host in the primary and
secondary sites. Remote Web Console computers must be installed in both of these sites. Also,
storage system settings must be made so that Business Continuity Manager can be used. For detailed
information about settings required for using volumes in a remote site, see the HP Business Continuity
Manager Software User's Guide.
If you use Business Continuity Manager, set the system option mode 762 to ON on the system that
has the host I/O time stamping function installed or the SYSPLEX timer is available. If Business
Continuiity Manager or an EXCTG is not being used, system option mode 762 must be set to OFF
for proper operation. For further information on system option mode, call HP technical support.
Up to four primary storage systems and up to four secondary storage systems can be used. For
example, you can use four primary storage systems and four secondary storage systems. Also,
you can use two primary storage systems and one secondary storage system.
The supervisor DKC and subordinate DKCs must be mutually connected at the secondary site, so
that arbitration processing can be performed. Also, remote command devices must be created in
the supervisor DKC. For details on secondary storage systems connections and remote command
devices, see the next section and the HP XP24000/XP20000 External Storage Software User's
Guide.
Connections Between Secondary Storage Systems
If you use more than one primary storage system and more than one secondary storage system,
you must establish connections among the secondary storage systems. To do this, you must configure
paths and ports. Also, you must create remote command devices by using XP External Storage.
The following figure is an example of connections among secondary storage systems.
64 Preparing for Universal Replicator for Mainframe Operations