Oracle Database Discussions

After setting up the physical standby database and configuring the Configuration, Fast_start failover and Observer, every things are OK. But after shutting down the primary database without first stopping the observer, the primary can not be opened(can only be mounted) an more. The fast_start failover cannot be disabled.
What should I do to repair it?
SQL> startup
ORACLE instance started.

Total System Global Area 448790528 bytes
Fixed Size 1219904 bytes
Variable Size 159384256 bytes
Database Buffers 281018368 bytes
Redo Buffers 7168000 bytes
Database mounted.
ORA-16649: database will open after Data Guard broker has evaluated Fast-Start
Failover status
DGMGRL> show configuration

Configuration
Name: sdb10g
Enabled: YES
Protection Mode: MaxAvailability
Fast-Start Failover: ENABLED
Databases:
sdb10g - Primary database
stdby10g - Physical standby database
- Fast-Start Failover target

Current status for "sdb10g":
Warning: ORA-16607: one or more databases have failed


DGMGRL> disable fast_start failover;
Error: ORA-12560: TNS:protocol adapter error

Failed.