HP StorageWorks XP Remote Web Console Software - Manual (Page 32)

• System. When the System timer option is selected, the primary storage system acquires the
time-stamp information for each journal data as follows. When a URz pair is established, the
primary storage system reports state-change-interrupt (SCI) to all hosts. The host then issues
a series of sense group commands to determine the device status change, and the primary
storage system returns the same response as if the device had been added to an XRC session to
activate I/O time-stamping for the device. Once I/O time-stamping is activated, the MVS IOS
routine attaches the time-stamp information (contents of time-of-day (TOD) clock) to each write
I/O operation for the device. The time-stamp indicates the time that the update was generated
during start sub-channel (SSCH) at the main host system, and the time-stamp is transferred to the
primary storage system at the beginning of each I/O operation.
• Local. When the Local timer option is selected, the primary storage system does not acquire
time-stamp information from the host I/O time-stamping function.
• None. This timer option can be selected only when the copy direction of a URz volume pair is in
reverse direction (i.e., from the secondary site to the primary site).
When the None option is selected, the primary storage system acquires time-stamp information from
the host I/O time-stamping function.
Journal Group Operations
URz provides the following group-based operations to simplify and expedite disaster or failure recovery
procedures:
• Group operations at the primary storage system
• Split all pairs in a journal group. See
“ Splitting a Mirror (Suspending a copy operation) ” on page 142
for a description of the Suspend Range-Group suspend pair option.
• Resume all suspended pairs in a journal group. See
“ Restoring a Mirror (Resuming a copy operation) ” on page 143 for a description of the URz
Resume Range-Group resume pair option.
• Release all pairs in a journal group. See
“ Deleting Data Volumes from a Mirror (Ending a copy operation) ” on page 144 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
“ Splitting a Mirror (Suspending a copy operation) ” on page 142 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
“ Deleting Data Volumes from a Mirror (Ending a copy operation) ” on page 144 for a
description of the Delete Range-Group delete pair option.
Read and Write I/O 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
32 Overview of Universal Replicator Operations