Oracle VM: Error - errcode=00001, errmsg=CDS accquire lock /etc/ovs-agent/db/cluster.lock

1. error message: 

 errcode=00001, errmsg=CDS accquire lock /etc/ovs-agent/db/cluster.lock timeout. locker process is NNNNN,

2. Solutions

is your storage repository on NFS?
And do you expirence short neworkt outage on the NFS storage maybe, before this error occurs?

You can try with the following workaround:
1) Stop all OVS-Agents: service ovs-agent stop
2) Delete the locks on the master: rm /OVS/.ovs-agent/db/*.lock
3) Start all OVS_Agents: service ovs-agent start

Or

Upgrade Oracle VM Server to 2.2.2 

When you upgrade Oracle VM server to 2.2.2, you should select "Oracle VM Server x.x.x (hda2) to upgrade from previous version. 
"Reinstall System" means newly install, not upgrade.

3. Useful link

Recommend to upgrade to 2.2.2 from https://forums.oracle.com/forums/thread.jspa?threadID=2270155