Hitachi MP-96RD625-01 manual Host I/O Time-Stamp

•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.

Chapter 2 About Universal Replicator Operations 2-17

Hitachi Universal Replicator for IBM /OS User’s Guide