ORA-16003: standby database is restricted to read-only access

dg失败导致，从库一直只能read only开启。

解决办法：

SQL> shutdown immediate

ORA-01109: database not open

Database dismounted.

ORACLE instance shut down.

SQL> startup nomount

ORACLE instance started.

Total System Global Area 1068937216 bytes

Fixed Size                  2235208 bytes

Variable Size             893387960 bytes

Database Buffers          167772160 bytes

Redo Buffers                5541888 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 1068937216 bytes

Fixed Size                  2235208 bytes

Variable Size             893387960 bytes

Database Buffers          167772160 bytes

Redo Buffers                5541888 bytes

Database mounted.

Database opened.

SQL> select open_mode from v4database;

select open_mode from v4database

                      *

ERROR at line 1:

ORA-00942: table or view does not exist

SQL> select open_mode from v$database;

OPEN_MODE

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