Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

Run this command only on recovery cluster nodes. This command succeeds only when
Continentalclusters is configured for maintenance mode. The command checks for the following
conditions to successfully disable a recovery group:
• The recovery package is down and package switching is disabled.
• The primary cluster and the primary package are up. If the cluster is down or unreachable,
use the force -f option to forcefully disable the recovery group.
WARNING! When you use the force option, ensure that the primary package and the cluster
are not down due to a primary site failure.
• The monitor package is up and running in the recovery cluster.
Moving a Recovery Group out of the Maintenance Mode
Run the following command to enable a recovery group and move it out of the maintenance mode:
cmrecovercl -e -g <recovery group>
Where:
<recovery group> is the name of the recovery group to be enabled and moved out of the
maintenance mode.
You can run this command only on recovery cluster nodes. The command succeeds only when
Continentalclusters is configured for maintenance mode. Following are the conditions that need to
be met for the recovery group to be enabled and moved out of the maintenance mode:
• For recovery groups configured with a rehearsal package, the rehearsal package is halted
and package switching is disabled.
• The monitor package is up and running in the recovery cluster.
Performing Cluster Recovery
When a CLUSTER_ALARM is issued, there may be a need for a cluster recovery using the recovery
command, cmrecovercl, which is enabled for use by the root user. Cluster recovery is carried
out at the site of the recovery cluster by using thecmrecovercl command. The cmrecovercl
command will only recover recovery groups that are enabled for recovery and are not in the
maintenance mode.
# cmrecovercl
Issuing this command will halt any configured data replication activity from the failed cluster to the
recovery cluster, and will start all configured recovery packages on the recovery cluster that are
pre-configured in recovery groups. A recovery group is the basic unit of recovery used in
Continentalclusters configuration. This command will fail if a cluster alarm has not been issued.
If option “-g RecoveryGroup” is specified with the recovery command, then the recovery process
of halting data replication activity and starting of the recovery package will only be done for the
specified recovery group.
After the cmrecovercl command is issued, there is a delay of at least 90 seconds (per recovery
group) while the command ensures that the package is not active on another cluster.
Cluster recovery is done as a last resort, after all other approaches to restore the unavailable cluster
have been exhausted. It is important to remember that cluster recovery sets in motion a process
that cannot be easily reversed. Unlike the failover of a package from one node to another, failing
a package from one cluster to another normally involves a significant quantity of data that is being
accessed from a new set of disks. Returning control to the original cluster will involve resynchronizing
this data and resetting the roles of the clusters in a process that is easier for some data replication
techniques than others.
44 Designing Continentalclusters