In an SF Oracle RAC cluster, the activation of shared disk groups should be set to "shared-write" on each of the cluster nodes.
To verify whether the "shared-write" activation is set:
# vxdg list dg_name |grep activation
local-activation: shared-write
If "shared-write" activation is not set, run the following command:
# vxdg -g dg_name set activation=sw