db816628_Data_Guard_11g___Using_DBMS_DG__Description
[Error] ORA-16817: unsynchronized Fast-Start Failover configuration [Description] 
DBMS_DG.INITIATE_FS_FAILOVER was invoked in a maximum available fast-start failover configuration when the configuration was not synchronized.
Mahir M. Quluzade | Oracle Blog: Oracle Data Guard 11g – Using DBMS_DG
Description