The online database command also includes a with standby_access option. Use for standby_access to bring a database online after loading it with a dump that was made using the with standby_access option.
WARNING! If you try to use online database for standby_access with a transaction log that was not dumped using the with standby_access option, the command fails.
The syntax for online database is:
online database database_name [for standby_access]
For more information about the with online database...for standby_access option, see the Reference Manual.