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

Maintenance mode for recovery groups is an optional feature. You must explicitly configure
Continentalclusters to use this feature. Consider the following guidelines when you move a recovery
group into the maintenance mode:
• Configure a shared disk with a file system in all primary clusters and in the recovery cluster.
This shared disk is local to the cluster and need not be replicated.
• Configure the CONTINENTAL_CLUSTER_STATE_DIR parameter in the Continentalcluster
configuration file with an absolute path to a file system. Create this path in all nodes and
reserve it for Continentalclusters. This file system is used to hold the current maintenance mode
setting for recovery groups.
• Configure the monitor package control script to mount the file system in the shared disk for
the path specified with the CONTINENTAL_CLUSTER_STATE_DIR parameter.
When a recovery group is in the maintenance mode, start up of a recovery package with
cmrecovercl, cmrunpkg or cmmodpkg commands is prevented by Continentalclusters for that
recovery group.
When a recovery group is in the maintenance mode there is no impact on the availability of the
primary packages. The primary package continues to be up and is highly available within the
primary cluster (i.e., local failover allowed). Clients can continue to connect to the primary package
and access its production data on the primary cluster.
There is no dependency on data replication to move a recovery group into maintenance mode.
Array based replication can be suspended or can be in progress. Similarly, logical replication
can either be suspended (receiver package is down) or can be resumed (receiver package is up).
Table 7 describes the impact on recovery when a recovery group is in the maintenance mode.
Table 7 Impact of Maintenance Mode
Maintenance ModeDefault Mode
Recovery package startup using cmrecovercl, cmrunpkg,
cmmodpkg or cmforceconcl commands is not allowed.
Recovery package startup using cmrecovercl,
cmrunpkg, cmmodpkg or cmforceconcl commands
is allowed.
No impact to primary packages. The primary package
continues to run irrespective of the mode.
Cross-checking is done between primary and recovery
packages to ensure both packages are not up at the
same time.
The primary package is allowed to start only if the
recovery package is down. Similarly, a recovery
package is allowed to start only if the primary package
is down.
Moving a Recovery Group into Maintenance Mode
Run the following command to disable a recovery group and move it into the maintenance mode:
cmrecovercl -d [-f] -g <recovery group>
Where:
<recovery group> is the name of the recovery group to be disabled.
Understanding Continentalclusters Concepts 43