openSUSE 13.1 NFSv4 Client - cannot read server files. Works OK if NFSv4 not selected.

I have a very simple setup with two machines on a private network. Same openSUSE13.1 on both. NFS setup with YaST. On the server side I export one directory named /z. I select the NFSv4 option without gss. Firewall is off on both systems. On the client side I want to mount /z (from the server) at mountpoint /z2. (I use IP addresses on both side; nfs domain is "localdomain".) When I select NFSv4 on the client side, I cannot see any files in /z (from the server side); my local /z2 directory is empty. When I do not select NFSv4 (or pNFSv4) on the client, but have NVSv4 on the server I can see the relevant files on the client machine.

How to I fix this?
------
I know it is bad form to ask two questions in one post, but where do I find a reasonable description of NFS (or NFSv4) management of files mounted in multiple client systems. If I update a file in one client, how are the other clients notified/protected/etc.

Bill Ogden