In this article, we are going to discuss how to freeze hosts in vcs. We need to understand why we have to freeze vcs cluster host. If you are performing any task like os patching or vcs related upgrade and your task need server reboot if you are not freezing cluster then automatic failover of service group takes place. So the freezing service group becomes critical to avoid failover of service groups to another active node in the cluster.
If the service group frozen cluster will keep monitoring resources in clusters but it will now allow making resources or service groups for online or offlining which prevents automatic failover of resources or service group. Freezing might be of two categories. It may be temporary or persistent. The impact of the temporary freeze will not be retained across reboots. For VCS configurations to remain in the same status persistent freeze is required.
We have considered here that you must be having already configured VCS related path in your .profile for commands to work without absolute path ie /etc/VRTS,/var/VRTSvcs & /opt/VRTSvcs has been included in your profile.
Temporarily Freezing Service Group
When we freeze the service group temporarily and if you restart VCS completely service group will automatically unfreeze on restart. To freeze and unfreeze the service group you can do using below command-line utilities.
# hagrp -freeze <SG> # hagrp -unfreeze <SG> Where <SG> stands for service group name.
How to freeze Persistently in VCS
As mentioned above this will freeze vcs host in event of reboot related need to avoid automatic failover of resources and resource group to another host in the cluster.
Freezing the Cluster Host Persistently
# hagrp -offline SG -sys system # Making SG offline. # haconf -makerw # Making configuration writable # hagrp -freeze SG –persistent # Freezing Persistently # haconf -dump -makero # Making configuration read-only.
Once you are done with your activity and reboot you need to unfreeze the service group with the persistent option only.
Unfreezing the Cluster Host Persistently
# haconf -makerw # Making configuration writable # hagrp -unfreeze SGSAPCI –persistent # Unfreezing Persistently # hagrp -online SG -sys system # Making SG online. # haconf -dump -makero # Making configuration read-only.
That,s it about how to freeze host in vcs to avoid automatic failover of service group to another host while performing any task on the host which required a reboot of the host.