HP StorageWorks XP Remote Web Console Software - Manual (Page 75)

Table 20 Specifications of Extended Consistency Groups
Item Specifications
The number of extended consistency groups that can be
created
Up to four per one storage system
The number of journal groups that can be registered in one
extended consistency group
Up to 16
The following explains configuration of extended consistency groups (i.e., primary and secondary
EXCTGs).
• Guaranteed Consistency of Data Update Sequence:
URz restores journal data to secondary data volumes by taking the following steps. The following
procedure guarantees consistency of data update sequence within an extended consistency group:
1. URz checks the extended consistency group for the time stamps of all journal data that have
not been restored to secondary data volumes, and then identifies the latest time stamp for
each journal group.
In the example shown in
Figure 18 on page 75, the latest time stamp for each journal group is
as follows:
• In Journal group 1, the latest time stamp is 15:00.
• In Journal group 2, the latest time stamp is 15:02.
• In Journal group 3, the latest time stamp is 15:03.
• In Journal group 4, the latest time stamp is 15:04.
1. URz searches for the oldest time stamp from the ones identified in step 1 on page 75 and
restores data up to that time to the secondary volumes.
In the example shown in
Figure 18 on page 75, the oldest time stamp is 15:00. URz restores all
data that have a time stamp 15:00 or earlier to the secondary data volumes.
• For Journal group 1, URz restores all data up to 15:00.
• For Journal group 2, URz restores all data up to 14:02.
• For Journal group 3, URz restores all data up to 14:03.
• For Journal group 4, URz restores all data up to 14:04.
Extended consistency group
15:00
14:00
13:00
12:00
15:02
14:02
13:02
12:02
15:03
14:03
13:03
12:03
15:04
14:04
13:04
12:04
Journal group 1 Journal group 2 Journal group 3 Journal group 4
indicates data that is to be restored to secondary data volumes
indicates data that is not to be restored to secondary data volumes
Legend:
Figure 18 Time Stamps of Data that Have Not Been Restored to Secondary
Data Volumes
• Consistency time:
In the URz windows, consistency times of extended consistency groups, journal groups, and data
volume pairs are displayed. These consistency times have the following meanings.
Hitachi Universal Replicator for z/OS user guide for XP12000/XP10000 Disk Arrays and SVS 200 75