Solutions to flashback standby database in oracle

How to open the standby database after Flashback:

SQL> flashback database to restore point myrs1;
 
Flashback complete.
 
SQL> shutdown immediate
ORA-01109: database not open
 
 
Database dismounted.
ORACLE instance shut down.
SQL> startup mount
ORACLE instance started.
 
Total System Global Area 521936896 bytes
Fixed Size 2254824 bytes
Variable Size 356517912 bytes
Database Buffers 159383552 bytes
Redo Buffers 3780608 bytes
Database mounted.
SQL>
SQL> alter database recover managed standby database using current logfile disconnect;
Alter database recover managed standby database using current logfile disconnect
*
ERROR at line 1:
ORA-01665: control file is not a standby control file
 
 
SQL>
SQL>
SQL> alter database convert to physical standby;
 
Database altered.
 
SQL>
SQL>
SQL> shutdown immediate
ORA-01109: database not open
 
 
Database dismounted.
ORACLE instance shut down.
SQL>
SQL>
SQL> startup
ORACLE instance started.
 
Total System Global Area 521936896 bytes
Fixed Size 2254824 bytes
Variable Size 356517912 bytes
Database Buffers 159383552 bytes
Redo Buffers 3780608 bytes
Database mounted.
Database opened.
SQL> alter database recover managed standby database using current logfile disconnect;
 
Database altered.
 
SQL>