Oracle Grid Infrastructure upgrade consists of upgrade of Oracle Clusterware and Oracle Automatic Storage Management (Oracle ASM).
Oracle Grid Infrastructure upgrades can be rolling upgrades, in which a subset of nodes are brought down and upgraded while other nodes remain active. Starting with Oracle ASM 12c release 2 (12.2), upgrades can be rolling upgrades.
You can also use Rapid Home Provisioning to upgrade Oracle Grid Infrastructure for a cluster.
rootupgrade.sh
script was run on all nodes, then the upgrade remains incomplete.