在只读模式下，数据文件及联机日志文件都禁止写操作。不过允许执行数据库恢复及其他不会产生回滚的操作。

数据库关闭的情况下

[oracle@prod1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Sun Feb 22 19:07:12 2015

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to an idle instance.

idle> startup open read only;
ORACLE instance started.

Total System Global Area 1383808 bytes
Fixed Size 1340104 bytes
Variable Size 658509112 bytes
Database Buffers 2292416 bytes
Redo Buffers 5042176 bytes
Database mounted.
Database opened.


idle> select open_mode from v$database;OPEN_MODE
--------------------READ ONLY

mount状态下

idle> alter database open read only;

Database altered.

重新恢复到读写状态

idle> shutdown immediate;
Database closed.Database dismounted.ORACLE instance shut down.idle> startup mount;
ORACLE instance started.Total System Global Area 1383808 bytesFixed Size 1340104 bytesVariable Size 658509112 bytesDatabase Buffers 2292416 bytesRedo Buffers 5042176 bytesDatabase mounted.idle> alter database open read write;

Database altered.

在只读模式下，数据文件及联机日志文件都禁止写操作。不过允许执行数据库恢复及其他不会产生回滚的操作。

数据库关闭的情况下

[oracle@prod1 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Sun Feb 22 19:07:12 2015

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to an idle instance.

idle> startup open read only;
ORACLE instance started.

Total System Global Area 1383808 bytes
Fixed Size 1340104 bytes
Variable Size 658509112 bytes
Database Buffers 2292416 bytes
Redo Buffers 5042176 bytes
Database mounted.
Database opened.


idle> select open_mode from v$database;OPEN_MODE
--------------------READ ONLY

mount状态下

idle> alter database open read only;

Database altered.

重新恢复到读写状态

idle> shutdown immediate;
Database closed.Database dismounted.ORACLE instance shut down.idle> startup mount;
ORACLE instance started.Total System Global Area 1383808 bytesFixed Size 1340104 bytesVariable Size 658509112 bytesDatabase Buffers 2292416 bytesRedo Buffers 5042176 bytesDatabase mounted.idle> alter database open read write;

Database altered.