Managing Serviceguard 14th Edition, June 2007

Cluster and Package Maintenance
Single-Node Operation
Chapter 7 383
Single-Node Operation
In a multi-node cluster, you could have a situation in which all but one
node has failed, or you have shut down all but one node, leaving your
cluster in single-node operation. This remaining node will probably have
applications running on it. As long as the Serviceguard daemon cmcld is
active, other nodes can rejoin the cluster.
If the Serviceguard daemon fails when in single-node operation, it will
leave the single node up and your applications running. (This is different
from the loss of the Serviceguard daemon in a multi-node cluster, which
halts the node with a TOC, and causes packages to be switched to
adoptive nodes.) It is not necessary to halt the single node in this
scenario, since the application is still running, and no other node is
currently available for package switching.
You should not try to restart Serviceguard, since data corruption might
occur if another node were to attempt to start up a new instance of the
application that is still running on the single node.
Instead of restarting the cluster, choose an appropriate time to shut
down the applications and reboot the node; this will allow Serviceguard
to restart the cluster after the reboot.