23ai版本支持用户级别设置read only特性,对于在某些情况下,为了数据的一致性,是一个比较方便的特性,而不是以前版本通过权限控制实现只读,比如授权create session+表/视图等查询权限
下面创建一个用户u_readonly,并授权dba权限,创建一个表进行测试

[oracle@xifenfei ~]$ ss

SQL*Plus: Release 23.0.0.0.0 - for Oracle Cloud and Engineered Systems on Sat Jan 11 21:12:09 2025
Version 23.5.0.24.07

Copyright (c) 1982, 2024, Oracle.  All rights reserved.


Connected to:
Oracle Database 23ai Enterprise Edition Release 23.0.0.0.0 - for Oracle Cloud and Engineered Systems
Version 23.5.0.24.07

SQL> 
SQL> select banner from v$version;

BANNER
--------------------------------------------------------------------------------
Oracle Database 23ai Enterprise Edition Release 23.0.0.0.0 - for Oracle Cloud an
d Engineered Systems


SQL> show pdbs;

    CON_ID CON_NAME                       OPEN MODE  RESTRICTED
---------- ------------------------------ ---------- ----------
         2 PDB$SEED                       READ ONLY  NO
         3 XIFENFEI                       MOUNTED
SQL> alter session set container=xifenfei;

Session altered.

SQL> alter database open;

Database altered.

SQL> create user u_readonly identified by oracle;

User created.

SQL> grant dba to u_readonly;

Grant succeeded.

SQL>  conn u_readonly/oracle@127.0.0.1/xifenfei
Connected.
SQL> create table t_xff as select * from dba_objects;

Table created.

SQL> select count(1) from t_xff;

  COUNT(1)
----------
     70951

修改用户为只读特性,然后进行dml/ddl操作会报ORA-28194: Can perform read operations only

SQL> conn / as sysdba
Connected.
SQL>  alter session set container=xifenfei;

Session altered.

SQL> alter user u_readonly read only;

User altered.

SQL> conn u_readonly/oracle@127.0.0.1/xifenfei
Connected.
SQL> delete from t_xff;
delete from t_xff
            *
ERROR at line 1:
ORA-28194: Can perform read operations only


SQL> insert into t_xff select * from dba_objects;
insert into t_xff select * from dba_objects
            *
ERROR at line 1:
ORA-28194: Can perform read operations only


SQL> select count(1) from t_xff;

  COUNT(1)
----------
     70951

SQL> create table t1 as select * from dba_users;
create table t1 as select * from dba_users
*
ERROR at line 1:
ORA-28194: Can perform read operations only

直接使用create user命令创建一个只读用户

SQL>  conn / as sysdba
Connected.
SQL> alter session set container=xifenfei;

Session altered.

SQL> create user u_readonly2 identified by oracle read only;

User created.

SQL> grant dba to u_readonly2;

Grant succeeded.

SQL>  conn u_readonly2/oracle@127.0.0.1/xifenfei
Connected.
SQL> create table t_xifenfei as select * from dba_objects;
create table t_xifenfei as select * from dba_objects
*
ERROR at line 1:
ORA-28194: Can perform read operations only

修改只读用户为读写模式

SQL> conn / as sysdba
Connected.
SQL>  alter session set container=xifenfei;

Session altered.

SQL> alter user u_readonly2 read write;

User altered.

SQL> conn u_readonly2/oracle@127.0.0.1/xifenfei
Connected.
SQL> create table t_xifenfei as select * from dba_objects;

Table created.

SQL> delete from t_xifenfei where rownum<100;

99 rows deleted.

SQL> commit;

Commit complete.

查看用户是否处于只读状态

SQL> select username,read_only from dba_users  where created>sysdate-1;

USERNAME                       READ_O
------------------------------ ------
U_READONLY2                    NO
U_READONLY                     YES

在只读用户中，使用动态plsql直接直接dml也报ORA-28194: Can perform read operations only

SQL> conn u_readonly/oracle@127.0.0.1/xifenfei
Connected.
SQL> select count(1) from t_xff;

  COUNT(1)
----------
     70951

SQL> delete from t_xff;
delete from t_xff
            *
ERROR at line 1:
ORA-28194: Can perform read operations only


SQL> DECLARE   
  2      v_sql VARCHAR2(1000);
  3  BEGIN
  4      v_sql := 'delete from t_xff where rownum<1000';
  5      EXECUTE IMMEDIATE v_sql;
  6  END;
  7  /
DECLARE
*
ERROR at line 1:
ORA-28194: Can perform read operations only
ORA-06512: at line 5

判断用户是否只读的底层基表属性user$.spare1

SQL> conn / as sysdba
Connected.
SQL> alter session set container=xifenfei;

Session altered.
SQL> COL NAME FOR A30
SQL>  select name,decode(bitand(spare1, 67108864), 67108864, 'YES', 'NO')
  2   read_only from user$ where name like 'U_READONLY%'
  3  /

NAME                           READ_O
------------------------------ ------
U_READONLY                     YES
U_READONLY2                    NO