SQL> startup mount
ORACLE instance started.
Total System Global Area 2466249080 bytes
Fixed Size 8898936 bytes
Variable Size 671088640 bytes
Database Buffers 1778384896 bytes
Redo Buffers 7876608 bytes
Database mounted.
SQL> alter database open read write;
alter database open read write
*
ERROR at line 1:
ORA-16003: standby database is restricted to read-only access
SQL>
SQL> shutdown immediate
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup nomount
ORACLE instance started.
Total System Global Area 2466249080 bytes
Fixed Size 8898936 bytes
Variable Size 671088640 bytes
Database Buffers 1778384896 bytes
Redo Buffers 7876608 bytes
SQL> alter database mount standby database;
Database altered.
SQL> alter database activate standby database;
Database altered.
SQL> shutdown immediate;
ORA-01109: database not open
Database dismounted.
ORACLE instance shut down.
SQL> startup open;
ORACLE instance started.
Total System Global Area 2466249080 bytes
Fixed Size 8898936 bytes
Variable Size 671088640 bytes
Database Buffers 1778384896 bytes
Redo Buffers 7876608 bytes
Database mounted.
Database opened.
SQL> select open_mode from v$database;
OPEN_MODE
--------------------
READ WRITE