HP StorageWorks XP Remote Web Console Software - Manual (Page 44)

2-22 Chapter 3 Preparing for Universal Replicator z/OS Operations
Hitachi Universal Replicator for IBM /OS User’s Guide
– Release all pairs in a journal group. See section Deleting Data Volumes
from a Mirror (Ending a copy operation) for a description of the Delete
Range-Group delete pair option.
• Group operations at the secondary storage system
– Split (suspend pair) all pairs in a journal group. See section Splitting a
Mirror (Suspending a copy operation) for a description of the Suspend
Range-Group suspend pair option.
– Release (delete pair) all pairs in a journal group regardless of their
consistency status. See section Deleting Data Volumes from a Mirror
(Ending a copy operation) for a description of the Delete Range-Group
delete pair option.
Read and Write I/O Operations During URz Operations
When a primary storage system receives a read I/O for a URz primary data
volume, the primary storage system performs the read from the primary data
volume. If the read fails, the redundancy provided by RAID-1 or RAID-5
technology recovers the failure. The primary storage system does not read the
URz secondary data volume for recovery.
When a primary storage system receives a write I/O for the primary data
volume with PAIR status, the primary storage system performs the update
copy operation, as well as writing to the primary data volume.
The primary storage system completes the primary data volume write
operations independently of the update copy operations at the secondary data
volume. The secondary storage system updates the data in the secondary data
volume according to the write sequence number of journal data. This will
maintain the data consistency between the primary and secondary data
volumes. If the primary data volume write operation fails, the primary storage
system reports a unit check and does not create the journal data for this
operation. If the update copy operation fails, the secondary storage system
suspends either the affected pair or all URz pairs in the journal group,
depending on the type of failure. When the suspended URz pair or journal
group is resumed (Resume Pair), the primary storage system and secondary
storage system negotiate the resynchronization of the pair(s). See section
Suspend Types for further information on URz suspend types.
During normal URz operations, the secondary storage system does not allow
URz secondary data volumes to be online (mounted), and therefore hosts
cannot read from and write to secondary data volumes. The URz secondary
data volume write enable option allows write access to a secondary data
volume while the pair is split (see the next section). The secondary data
volume write option can only be enabled when you split the pair from the
primary storage system.