In order to perform a switchover all sessions to the database need to be
disconnected. In version 901 this was a manual process. In version 9.2.0
this process has been automated with the “with session shutdown” clause
that has been added to the alter database commit to switchover command.
If SWITCHOVER_STATUS returns SESSIONS ACTIVE then you should either
disconnect all sessions manually or when performing step 2 you should append
the “with session shutdown” clause. For example:
SQL> alter database commit to switchover to standby with session shutdown;
Read manuls before you do and also metalink note 232240.1