We’ve had issues with RAC one-node and OEM for a very long time. One really vexing issue has to do with incorrect instance status after a relocation.
EM12c: Scan Listener Shows Down Status In EM Console After Relocation (Doc ID 1932744.1) has instructions for fixing the issue. It boils down to this:
There is an OMS parameter called oracle.sysman.db.rac.ReconfigProcessingEnable that is not set under normal circumstances for Real Application Clusters because a OEM doesn’t need to keep track of which instance number is running on which host. For R1 it’s a big deal.
The process boiled down to this:
On the OMS server, execute:
emctl set property -name oracle.sysman.db.rac.ReconfigProcessingEnable -value true emctl get property -name oracle.sysman.db.rac.ReconfigProcessingEnable
Bounce the OMS server to pick up the configuration change.
If some of the systems still look like they’re having the instance-awareness problem run a clearstate on the remote host
emctl stop agent emctl clearstate agent emctl start agent emctl upload agent