HP StorageWorks XP Remote Web Console Software - Manual (Page 25)

Remote Copy Operations
The following figure illustrates the two types of Universal Replicator for Mainframe remote copy
operations: initial copy and update copy.
Figure 5 Remote Copy Operations
This section describes the following topics that are related to remote copy operations with Universal
Replicator for Mainframe:
•
Initial copy operation (see the next section)
•
Update copy operation
•
Read and write I/O operations for Universal Replicator for Mainframe volumes
•
Secondary data volume write option
•
Secondary data volume read option
•
Difference management
Initial Copy Operation
Initial copy operation synchronizes data in the primary data volume and data in the secondary
data volume. An initial copy operation is performed independently from host I/Os. An initial copy
operation is performed when you create a data volume pair or when you resynchronize a suspended
pair. The initial copy operation copies the base-journal data that is obtained from the primary data
volume at the primary storage system to the secondary storage system, and then restores the
base-journal to the secondary data volume.
If the journal-obtain operation starts at the primary data volume, the primary storage system obtains
all data from the primary data volume as the base-journal data, in sequence. The base-journal
contains a replica of the entire data volume or a replica of updates to the data volume. The
base-journal will be copied from the primary storage system to the secondary storage system after
the secondary storage system issues a read-journal command. After a base-journal is copied to
the secondary storage system, the base-journal will be stored in a restore journal volume in a
restore journal group where the secondary data volume belongs. After that, the data in the restore
journal volume will be restored to the secondary data volume, so that the data in the secondary
data volume synchronizes with the data in the primary data volume.
The base-journal data is stored in the entire data volume or the area for the difference. The area
for the difference is used when the difference resynchronization operation is performed. The journal
data for the entire data volume is created when the data volume pair is created. The difference
journal data is obtained when the pair status of the data volume changes from Suspending status
to Pair resync status. Merging the difference bitmaps that are recorded on both primary and
secondary data volumes enables you to obtain the journal data for only the difference. When a
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