HP StorageWorks XP Remote Web Console Software - Manual (Page 39)

Chapter 2 About Universal Replicator Operations 2-17
Hitachi Universal Replicator for IBM /OS User’s Guide
• If a pair in Journal group 4 is suspended, the consistency time will
be 14:04.
If a failure occurs in a primary storage system and then you wish to
recover from the failure, please restore journal data with time stamps later
than the consistency time of the extended consistency group to secondary
data volumes. For example, in the case described in Figure 2-4, the
consistency time of the extended consistency group is 15:00, and therefore
you must restore the following data to secondary data volumes.
• Data with the time stamp 15:02 in journal group 2
• Data with the time stamp 15:03 in journal group 3
• Data with the time stamp 15:04 in journal group 4
If a failure occurs in a secondary storage system and then you wish to
recover from the failure, please compare the consistency times of all
journal groups in the extended consistency group, and then identify the
oldest consistency time. Next, please restore all data with time stamps
later than the oldest consistency time, to the secondary data volume. For
example, in the case described in Figure 2-4, the consistency time of
journal group 2 is the oldest among journal groups 1 to 4. Since the
consistency time of journal group 2 is 14:02, you must restore the
following data to secondary data volumes.
• Data with the time stamp 15:00 in journal group 1
• Data with the time stamp 15:02 in journal group 2
• Data with the time stamp 14:03, and data with the time stamp
15:03 in journal group 3
• Data with the time stamp 14:04, and data with the time stamp
15:04 in journal group 4
Host I/O Time-Stamp
If you plan to establish URz journal groups, the I/O time-stamping function
must be installed on the host processor at the primary site. The I/O time-
stamp, which is provided by MVS DFSMSdfp, is the same time-stamp that is
used by Compatible XRC pairs. The I/O time-stamping function should also be
installed on the host processor at the secondary site, so that time-stamps can
be used when copying data in the reverse direction.
Note: If the system at the primary and/or secondary site consists of several
CPU complexes, a SYSPLEX timer is required to provide a common time
reference for the I/O time-stamping function.