Cause: There was a mismatch in configuration unique ID. This could occur if the original configuration was re-created while this database was disconnected from the network or the same database was added to two different Data Guard broker configurations. See the solution below.

Error solution: Make sure the database belongs to only one broker configuration. Shut down the broker by setting the DG_BROKER_START initialization parameter to false. Then remove the Data Guard broker configuration files. Finally restart the broker by setting the DG_BROKER_START initialization parameter to true.