HP StorageWorks XP Remote Web Console Software - Manual (Page 89)

• When you execute split operation, the URz pair status must be duplex, and the SIz pair status
must be either duplex or pending. If the status of the URz pair or the SIz pair is suspended
due to a failure, the journal data which was created before the split time may not be restored
to the SIz T-VOL after the split operation has been completed.
• The split time and the actual starting time of the split operation are not necessarily the same.
The starting time of the split operation will delay depending on the amount of journal data
stored in the journal volume at the split time. For example, if journal data that needs one hour
to be completely restored is stored at the split time, the starting time of the split operation will
delay for one hour.
• Even if the specified timeout period has passed from the split time, journal data with the time
stamp later than the split time may not be detected due to some reason such as a lot of journal
data stored in the journal volume. If the journal data with such a time stamp cannot detected,
the split operation of SIz pair will be executed after the specified timeout period. Since the
time out value is variable, please set the value according to your environment. The default
time out value is 6 hours. For a guide to set the time out value, please refer to the Guideline
for the Timeout Menu Setting When Using At-Time Split Function at Combining Universal
Replicator with ShadowImage. For details on how to specify a timeout value, please refer to
the Business Continuity Manager™ User’s Guide.
Caution — If you use the At-Time Split function when combining URz with SIz, note the following:
• The specified split time is enabled even after the split operation has been executed on SIz
pair. When you execute split operation again on ShadowImage for z/OS consistency group
that has been split before, specify the split time after deleting the split time registered before.
• In cascading configuration of URz and Hitachi TrueCopy for z/OS, the At-Time Split function
cannot be used for SIz pairs in conjunction with URz S-VOLs.
• In Multi-target configuration of URz and Hitachi TrueCopy for z/OS, when the At-Time Split
function is used for SIz pairs in conjunction with URz S-VOLs, please mind the following: when
URz and Hitachi TrueCopy for z/OS are configured in a cascading configuration during
disaster recovery operation, the At-Time Split function cannot be used.
• The specified split time will be reset by executing PS OFF of RCU.
• You cannot execute Reverse Resync of URz when split time is already specified. Please execute
Reverse Resync after you delete all the specified split time of SIz pairs in conjunction with the
restore journal group. For details on Reverse Resync, please refer to the Business Continuity
Manager™ User’s Guide.
• When split time is set to ShadowImage for z/OS consistency group, you cannot perform Add
Pair operation, Pair Resync operation, or Split Pair operation from the Business Continuity
Manager. If you need to execute Add Pair operation, Pair Resync operation, or Split Pair
operation, please delete the split time in advance. When split time is set to ShadowImage
for z/OS consistency group, pairs can be deleted. If you delete the following pairs, the
specified split time will be deleted:
Delete all the SIz pairs belonging to the ShadowImage for z/OS consistency group. Delete all the
URz pairs belonging to the URz restore journal group.
Combining URz with TCz Synchronous (3DC Cascading Configuration)
The XP storage system provides the function to combine URz and TCz Synchronous. This combination is
intended to ensure that the response time against host I/Os is comparable, regardless of whether the
distance between the primary and the secondary sites are short or long. This combination is also
intended to ensure that the secondary site stores data that has been stored in the primary site even
when a failure occurs in the primary site. These intentions will be fulfilled if remote copy operations
are performed using cascading connections and a three data center (3DC) configuration; in a 3DC
configuration, an intermediate site is located between the primary and secondary sites.
Figure 35 on page 90 shows an example of a 3DC cascading configuration in which URz and TCz
Synchronous are combined. In this configuration, the volume in the primary site is a TCz Synchronous
main volume (M-VOL). The corresponding TCz Synchronous remote volume (secondary data volume)
is the volume in the intermediate site, which is within a short distance from the primary site. This TCz
Synchronous remote volume is also used as a URz primary data volume. The corresponding URz
Hitachi Universal Replicator for z/OS user guide for XP12000/XP10000 Disk Arrays and SVS 200 89