7-8 Chapter 7 Using Extended Consistency Groups
Hitachi Universal Replicator for IBM /OS User’s Guide
You can remove journal groups from an extended consistency group
anytime, regardless of the status of the journal groups. Also, if you delete
all data volumes from a journal group in an extended consistency group,
the journal group will automatically be removed from the extended
consistency group.
Removal of journal groups from an extended consistency group does not
stop remote copy operations, but does affect consistency in data update
sequence. In the example in
Figure 7-2 below, if you remove the journal
group 1 from the secondary EXCTG, the remote copy operation from the
primary storage system 1 to the secondary storage system 1 will continue.
However, consistency in data update sequence will only be maintained
among the primary storage systems 2 and 3 and the secondary storage
systems 2 and 3.
Primary host
Primary EXCTG
Master JNL VOL
Secondary EXCTG
Primary subsystem 1
Primary data
volume
Write data
Master JNL VOL
Primary data
volume
Master JNL VOL
Primary subsystem 3
Primary data
volume
Secondary data
volume
Restore JNL VOL
Secondary subsystem 1
Secondary data
volume
Restore JNL VOL
Secondary subsystem 2 Primary subsystem 2
Secondary data
volume
Secondary subsystem 3
Journal group 1
Journal group 1
Journal group 2
Journal group 2
Journal group 3
Journal group 3
Restore JNL VOL
Figure 7-2 Example 1: Remote Copy Operations Among Three
Primary Storage Systems and Three Secondary Storage
Systems
