HP StorageWorks XP Remote Web Console Software - Manual (Page 78)

Disaster Recovery for Multiple Primary and Secondary Storage Systems
Consistency of Data Update Sequence When a Disaster Occurs
When a failure occurs in some primary or secondary storage system, all journal groups in the extended
consistency group will be suspended and remote copy operations will be suspended. The consistency
of data update sequence will be maintained if a failure occurs in a primary storage system, but the
consistency will not be maintained if a failure occurs in a secondary storage system.
For example, in the case described in
Figure 20 on page 78, if a failure occurs in the primary storage
system 1 at 10:00 a.m., journal groups 1 to 3 will be suspended due to the failure, and the data written
from the host before 10:00 a.m. will be restored to secondary data volumes in the secondary EXCTG,
while consistency of data update sequence is maintained. On the other hand, if a failure occurs in
the secondary storage system 1, journal groups 1 to 3 will be suspended due to the failure, and the
consistency of the data update sequence will not be maintained for secondary data volumes in the
extended consistency group.
Write data
Primary host
Extended consistency group
Master JNL VOL
Primary storage system 1
Primary data
volume
Master JNL VOL
Primary data
volume
Master JNL VOL
Primary storage system 3
Primary data
volume
Secondary data
volume
Restore JNL VOL
Secondary storage system 1
Secondary data
volume
Restore JNL VOL
Secondary storage system 2 Primary storage system 2
Secondary data
volume
Secondary storage system 3
Journal group 1 Journal group 1
Journal group 2 Journal group 2
Journal group 3 Journal group 3
Restore JNL VOL
Figure 20 Example 2: Remote Copy Operations Among Three Primary Storage
Systems and Three Secondary Storage Systems
Disaster Recovery Procedure
The following is an example of the procedure that should be followed when a disaster or failure occurs in
the primary site in multi-primary and multi-secondary storage systems configuration:
1. Switch operations from the primary site to the secondary site.
2. Reverse the copy direction, so that data are copied from the secondary site to the primary site.
78 Preparing for Universal Replicator z/OS Operations