Opening a Standby Database For Read Only Access.

Open a standby database for read-only access when

it is currently performing redo apply.

SQL> alter database recover managed standby database cancel;

Database altered.

SQL> alter database open;

Database altered.

SQL>

Change the standby database from being open for read 

only to performing redo apply.

SQL> alter database recover managed standby database

 disconnect from session;

Database altered.