How to set Oracle database read-only

Method: 1. Use the "ALTER DATABASE MOUNT;" statement to set the database to Mount mode; 2. Use the "alter database open read only;" statement to set the database to read-only. When the database is set to read-only status, users can only query data.

The operating environment of this tutorial: Windows 10 system, Oracle 11g version, Dell G3 computer.

How to set oracle database read-only

1. Switch from NoMount mode to Mount mode (there is no switch from mount to nomount):

Command :

ALTER DATABASE MOUNT;

mount: In the nomount phase, you can switch to the mount phase by reading the control file. During the database loading phase (mount), the names and locations of all data files and online log files are read from the control file, but these files are not actually searched.

At this stage, the operations that can be performed are: database log archiving, database media recovery, bringing data files online or offline, relocating data files and online log files.

startup command is equivalent to:

2. Read-only status

Set read-only command:

alter database open read only;

When a normally opened database is set to read-only status, users can only query data, but cannot modify database objects in any way. Being in a read-only state may ensure that the contents of data files and redo log files are not modified, but does not restrict operations that do not write data files and redo log files.

Supplement: It is definitely not easy to change the database to READ ONLY after OPEN. It must be changed under MOUNT

Expand knowledge:

Detailed explanation of switching between Oracle startup modes and restricted status and read-only status

Use the Alter Database statement to switch between startup modes.

1. Switch from NoMount mode to Mount mode (without switching from mount to nomount):

Command: ALTER DATABASE MOUNT;

2. When the database status is closed When in Open mode, switch to Open mode

Command: ALTER DATABASE OPEN;

3. In Open mode, you can also choose to set the database to unrestricted state and restricted state.

Command:

When starting Open mode, add the restrict keyword: startup restrict

Set or cancel the restricted state: alter system enable\disable restricted session;

Explanation:

The unrestricted state is the state we usually use in application development.

Restricted state, when the open database is set to the restricted state, only users with Create Session and Restricted Session system permissions or with SYSDBA and SYSPORE system permissions can connect to the database. However, after entering the restricted state, there may still be active normal user sessions in the system.

Restricted status usage:

(1) Perform data import or export operations;

(2) Temporarily deny ordinary users access to the database;

( 3) Perform database migration or upgrade operations.

Recommended tutorial: "Oracle Video Tutorial"

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