Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Cascading Failover in a Continental Cluster
Data Replication Procedures
Chapter 8382
always be behind. The level of data currency on the recovery Symmetrix
is dictated by the frequency at which it is refreshed. The refresh process
is shown in Figure 8-9.
Figure 8-9 Data Refresh in Steady State
The following procedure describes the steps necessary to periodically
copy the data from the secondary Symmetrix to the recovery Symmetrix
while the application is running on the primary site.
1. Freeze the application I/O to prevent the application from writing
data to the R1 devices in the primary Symmetrix. The method of
freezing the I/O is application dependent.
2. Use the following command to check the state of the SRDF link from
the R1 devices in the primary Symmetrix to the R2 devices in the
secondary Symmetrix. Make sure that the state is “Synchronized”
before executing step 3.
# symrdf -g <prisymdevgrpname> query
3. Split the BCV/R1 devices in the secondary Symmetrix from the
mirror group:
# symmir -g <prisymdevgrpname> split -rdf
4. Resume the application I/O to the R1 devices in the primary
Symmetrix if needed. The method of resuming the I/O is application
dependent.