ORA-16693: requirements not met for enabling fast-start failover

1.Fast star failover mode is not enabled, even the logxptmode of both the standby and primary database ins async as per the protection mode requirement of maxprotection mode.

DGMGRL>  enable fast_start failover
Error: ORA-16693: requirements not met for enabling fast-start failover
Failed.
DGMGRL> show database orcl_us logxptmode
  LogXptMode = 'ASYNC'
DGMGRL> show database orcl_in logxptmode
  LogXptMode = 'ASYNC'
DGMGRL> show database 'orcl_us'

Database - orcl_us

  Role:              PHYSICAL STANDBY
  Intended State:    APPLY-ON
  Transport Lag:     0 seconds (computed 1 second ago)
  Apply Lag:         0 seconds (computed 1 second ago)
  Apply Rate:        83.00 KByte/s
  Real Time Query:   ON
  Instance(s):
    orcl2

Database Status:
SUCCESS

2.The dataguard logs message shows the flashback mode is not enabled in target standby

version check on database orcl_us detected stale metadata,
      requesting update from primary database
Creating process RSM0
07/28/2014 12:42:29
ORA-16693, FSFO requires the target standby to be in flashback mode

3.Enabled the flashback mode in standby database

DGMGRL> connect sys/sys123@orcl_us
Connected as SYSDBA.

DGMGRL> edit database 'orcl_us' set state='apply-off';
Succeeded.
DGMGRL>  sql "alter database flashback on";
Succeeded.
DGMGRL> enable fast_start failover
Enabled.
DGMGRL> edit database 'orcl_us' set state='apply-on';
Succeeded.
DGMGRL> show configuration

Configuration - broker1

  Protection Mode: MaxPerformance
  Databases:
  orcl_in - Primary database
    Warning: ORA-16819: fast-start failover observer not started

    orcl_us - (*) Physical standby database
      Warning: ORA-16819: fast-start failover observer not started

Fast-Start Failover: ENABLED

Configuration Status:
WARNING

4. Fast start failover is enabled, with a warning message of observer process is not started.