Oracle database: Flashback and activate standby database for read/write 10g

------------------- Switching to DR
DR:
alter system set db_recovery_file_dest='/u03/flash_recovery_area';
alter system set db_recovery_file_dest_size=32g;
alter system set db_flashback_retention_target=1440;
alter database recover managed standby database cancel;
alter database flashback on;
alter database recover managed standby database cancel;
select open_mode from v$database;
create restore point before_open_standby guarantee flashback database;
select scn, time, name from v$restore_point where name = 'before_open_standby';

Primary
alter system set log_archive_dest_state_2=defer;
alter system switch logfile;

DR:
alter database activate standby database;
startup mount force;
alter database set standby database to maximize performance;
alter database open;  

Primary:
alter system set log_archive_dest_state_2=defer;

--------------------- Revert the snapshot database to physical standby
DR:
startup mount force;
flashback database to restore point before_open_standby;
alter database convert to physical standby;
startup mount force;
drop restore point before_open_standby;

Primary
alter system set log_archive_dest_state_2=ENABLE
alter database recover managed standby database using current logfile disconnect;