HP StorageWorks XP Remote Web Console Software - Manual (Page 12)

Figure 1 Universal Replicator for Mainframe Components for a Fibre Channel Connection
Journal Obtain
Journal obtain is the function to store the already stored data in the primary data volume as a
base-journal in the journal volume at the primary site. This function then stores the write data as a
journal data in the journal volume with every update of the primary data volume according to the
write instruction from the host. The journal obtain operation is performed according to the instruction
of the add pair or Resume Pair operation from the primary site. The write sequence number from
the host is assigned to the journal data. According to this information, the write sequence consistency
at the secondary site can be maintained. The update data from the host is kept in the cache.
Therefore, the journal obtain function for the update data is performed asynchronously from the
time the storage system receives the update data from the host until it stores the update data to the
data volume.
Journal Copy
Journal copy is the function to copy the data in the master journal volume at the primary site to the
restore journal volume at the secondary site. The secondary storage system issues the read journal
command to the primary storage system to request a transfer of the data that is stored in the master
journal volume according to the pair create or Resume Pair operation instruction from the primary
site. The primary storage system transfers the data in the journal volume to the secondary site
according to the read journal command if it has the journal data that should be sent. If the primary
storage system does not have the journal data, the information is sent. The secondary storage
system stores the journal volume data that is sent from the primary site in the restore journal volume
at the secondary site. The read journal commands are issued repeatedly and regularly from the
secondary site to the primary site until the journal operation is stopped. After the data are restored,
the journal sequence numbers are sent from the secondary site to the primary site when the read
journal command is issued. According to this information, the journal data at the primary site are
discarded.
Journal Restore
Journal restore is the function to reflect the stored data in the restore journal volume to the secondary
data volume at the secondary site. The data in the restore journal volume are restored to the
secondary data volume according to the write sequence number. This will ensure the write sequence
12 About Universal Replicator for Mainframe Operations