Manual GAB membership seeding
It is possible that one of the nodes does not come up when all the nodes in the cluster are restarted, due to the "minimum seed requirement" safety that is enforced by GAB. Human intervention is needed to safely determine that the other node is in fact not participating in its own mini-cluster.
The following should be carefully validated before manual seeding, to prevent introducing split-brain and subsequent data corruption:
Verify that none of the other nodes in the cluster have a port "a" membership
Verify that none of the other nodes have any shared disk groups imported
Determine why any node that is still running does not have a port "a" membership
Run the following command to manually seed GAB membership:
# gabconfig -cx
Refer to gabconfig (1M) for more details.