db816628_Data_Guard_11g___Using_DBMS_DG__Description
[Error] ORA-16819: Fast-Start Failover observer not started [Description] 
DBMS_DG.INITIATE_FS_FAILOVER was invoked but an observer had not yet been started.
Mahir M. Quluzade | Oracle Blog: Oracle Data Guard 11g – Using DBMS_DG
Description