SQL> show parameter o7

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
O7_DICTIONARY_ACCESSIBILITY boolean FALSE
SQL> create user test1 identified by test1;

User created.

SQL> grant connect,select any table to test1;

Grant succeeded.

open others window to logon:

SQL> conn test1/test1@testdb
Connected.
SQL> select count(*) from user_tables;

COUNT(*)
----------
0

SQL> select count(*) from dba_tables;
select count(*) from dba_tables
*
ERROR at line 1:
ORA-00942: table or view does not exist

SQL> select count(*) from v$session;
select count(*) from v$session
*
ERROR at line 1:
ORA-00942: table or view does not exist;

Explicit grant privilege to test1;

SQL> grant select on dba_tables to test1;

Grant succeeded.

SQL> grant select on v_$session to test1;

Grant succeeded.

test1 window:

SQL> select count(*) from dba_tables;

COUNT(*)
----------
816

SQL> select count(*) from v$session;

COUNT(*)
----------
13

Set .parameter value=true;

SQL> show parameter o7

NAME TYPE VALUE
------------------------------------ ----------- -----------
O7_DICTIONARY_ACCESSIBILITY boolean TRUE
SQL> create user test2 identified by test2;

User created.

SQL> grant connect ,select any table to test2;

Grant succeeded.

SQL>

SQL> conn test2/test2@testdb
Connected.
SQL> select count(*) from user_tables;

COUNT(*)
----------
0

SQL> select count(*) from dba_tables;

COUNT(*)
----------
816

SQL> select count(*) from v$session;

COUNT(*)
----------
10

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select any dictionary系统权限可以override O7_DICTIONARY_ACCESSIBILITY=false的情况去访问系统数据字典