The crsctl start rollingupgrade command transitions Oracle Clusterware and Oracle ASM into rolling upgrade mode.
This command queries the Oracle Clusterware rolling upgrade state and Oracle ASM cluster state. If either one is not in rolling upgrade mode, it will use the appropriate method to transition Oracle Clusterware or Oracle ASM to rolling upgrade mode.
If Oracle Clusterware and Oracle ASM are both in rolling upgrade mode when you run this command, then this command does nothing.
The rolling upgrade mode is not persistent. If all the nodes in a cluster are shut down and restarted, then the cluster transitions out of rolling upgrade mode when it is restarted. Similarly, if Oracle Clusterware is stopped and then restarted on all nodes in the cluster, then the rolling upgrade mode is lost.
This command does not transition Oracle ASM to rolling upgrade mode if run within an Oracle ASM Client Cluster.