ORA-01665: control file is not a standby control file

Today was the task : open physical standby database in read-write mode, do the write test on it and revert it back to physical standby.

I enabled flashback database on standby, open it and flashed back.
But after flashback the standby don't want to back to its standby state:

RMAN> flashback database to restore point yu1;

Starting flashback at 13.07.2012 07:19:26
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=1 device type=DISK


starting media recovery
media recovery complete, elapsed time: 00:00:01

Finished flashback at 13.07.2012 07:19:29
 

...

RMAN> sql 'alter database mount standby database';

using target database control file instead of recovery catalog
sql statement: alter database mount standby database
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of sql command on default channel at 07/13/2012 07:21:45
RMAN-11003: failure during parse/execution of SQL statement: alter database mount standby database
ORA-01665: control file is not a standby control file

The solution for this problem is:

ALTER DATABASE CONVERT TO PHYSICAL STANDBY DATABASE;