HP StorageWorks XP Remote Web Console Software - Manual (Page 30)

which results in an IEA491E system console message. This information should be transferred to the
primary site via the ERC for effective disaster detection and recovery.
Remote Copy Operations
Figure 4 on page 30 illustrates the two types of URz remote copy operations: initial copy and update
copy.
Primary host
Obtaining updated
journal data
Update copy
Write instruction
Secondary host
Initial copy
Obtaining base-journal
Primary storage system Secondary storage system
Restore
Secondary
data
volume
Restore
journal
volume
Primary
data
volume
Master
journal
volume
Figure 4 Remote Copy Operations
This section describes the following topics that are related to remote copy operations with URz:
• Initial copy operation (see the next section)
• Update copy operation
• Read and write I/O operations for URz volumes
• Secondary data volume write option
• Secondary data volume read option
• Difference management
Initial Copy Operations
Initial copy operations synchronize data in the primary data volume and data in the secondary data
volume. Initial copy operations are performed independently from host I/Os. Initial copy operations
are 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 of 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.
30 Overview of Universal Replicator Operations