Using NFS in RAC or non-RAC environment without proper security settings at the NFS server side may lead to 'permission denied' for a process trying to access a file, even for read, as root. The necessary bits may be set to allow read, write and execute for the file at user and group level if the NFS share was not granted root, read and/or write permission, there may be problems performing these operation.
At the NFS server side, the share of a particular directory needs to be done with root permission specified and for read and or write.
This needs to be fixed by the system administrator, the mount may need to be dropped by the client and then re-mapped for the permissions to take effect The NFS server daemons may also need to be restarted. Here is an example for HP-UX: