Ans : Required unlock to modify the files by stopping the clusterware stack while patching.
When you run the rootcrs.pl script with the -unlock flag, it stops the Oracle Clusterware stack and unlocks the files in the Grid home so they can be modified.
perl rootcrs.pl -unlock -crshome /u01/app/11.2.0/grid
rootcrs.pl script with the
-patch flag locks the Grid home again and restarts the Oracle Clusterware stack.