Given a 2 node domain, what option do you have to allow a single node to obtain Operational Quorum after bringing one node offline and knowing your TieBreaker device will not be accessible from the surviving node ?
Firstly, if you want to know more about "Quorum", check out one of my earlier blogs:
There are a number of scenarios where clients have ended up with a surviving node unable to obtain quorum during various maintenance activities. There is a way to avoid the dependency on the quorum device (for example a network TieBreaker) during a period where you know there will be network outages or node outages, or at the very least problems reserving the TieBreaker.
The simple solution being offered here is to exploit one of the default TieBreakers, known as the "Operator" TieBreaker.
You can list the TieBreakers defined in your domain using the following command :
You should see one called "Operator" as its created by default when the domain was first created.
You can check which TieBreaker is the current active TieBreaker using the following command
lsrsrc -c IBM.PeerNode
... check the attribute "OpQuorumTieBreaker"
Now to allow for the most flexibility during times of maintenance, you could change your active TieBreaker to the "Operator" TieBreaker.
But here's the thing ... you can only change the active TieBreaker when you have Configuration Quorum ... this means in a 2 node domain, both nodes need to be online before you do this. This should make it very clear that such a change would need to be done in advance of a quorum problem. What is being offered here is not a means of restoring quorum after you find your domain in a pending or no quorum state [if you are in this predicament, call Support and we'll see what we can offer for your individual situation ].
Lets assume you read this blog in advance of your planned maintenance activities and had the chance to change the active TieBreaker to "Operator" before breaking anything. You would use the following command to make such a change :
chrsrc -c IBM.PeerNode OpQuorumTieBreaker=Operator
.... again it assumes both nodes are online.
With the active TieBreaker set to "Operator", the next time you shutdown (or isolate) one node, the remaining node can be changed from "Pending Quorum" to "Has Quorum" manually using the following command :
runact -c IBM.PeerDomain ResolveOpQuorumTie Ownership=1
Note: the surviving node would remain Pending Quorum until you run the above command.
For more details about explicitly resolving a tie when the active TieBreaker is set to Operator:
Once you are finished with your testing, and with both nodes back online, you can change the active TieBreaker back to your usual TieBreaker :
chrsrc -c IBM.PeerNode OpQuorumTieBreaker=<Name_of_your_Network_TieBreaker>