After installation, if you need to modify the Oracle Clusterware configuration, then you must unlock the Grid home.

For example, if you want to apply a one-off patch, or if you want to modify an Oracle Exadata configuration to run IPC traffic over RDS on the interconnect instead of using the default UDP, then you must unlock the Grid home.
Unlock the home using the following procedure:

1.
Change directory to the path Grid_home/crs/install, where Grid_home is the path to the Grid home, and unlock the Grid home using the command rootcrs.pl -unlock -crshome Grid_home, where Grid_home is the path to your Grid infrastructure home.
For example, with the grid home /u01/app/11.2.0/grid,
enter the following command:
# cd /u01/app/11.2.0/grid/crs/install
# perl rootcrs.pl -unlock -crshome /u01/app/11.2.0/grid

2.
Change user to the grid infrastructure software owner, and relink binaries using the command syntax make -f Grid_home/lib/ins_rdbms.mk target, where Grid_ome is the Grid home, and target is the binaries that you want to relink.
For example, where the grid user is grid, $ORACLE_HOME is set to the Grid home, and where you are updating the interconnect protocol from UDP to IPC, enter the following command:
# su grid
$ make -f $ORACLE_HOME/lib/ins_rdbms.mk ipc_rds ioracle

Caution: Before relinking executables, you must shut down all executables that run in the Oracle home directory that you are relinking. In addition, shut down applications linked with Oracle shared libraries.
Note: To relink binaries, you can also change to the grid installation owner and run the command Grid_home/bin/relink.

3.
Relock the Grid home and restart the cluster using the following command:
# perl rootcrs.pl -patch

4. Repeat steps 1 through 3 on each cluster member node.