如何理解Oracle中“通过角色授权”需要用户重新登陆

1,DBA做如下的操作:

create user u1 identified by u1

create role r1;

grant create session to r1;

grant r1 to u1;

通过查询 select * from dba_sys_privs where grantee='R1',发现权限已经付给了角色.

通过查询 select * from dba_role_privs where grantee='U1',发现角色r1已经付给了用户u1.

R1

3,u1尝试建表:没有建表的权限.

SQL> create table t(i int);
create table t(i int)
*
ERROR at line 1:
ORA-01031: insufficient privileges

4,DBA建立另外一个角色r2,授予r2建表的权限,建r2授予u1.

create role r2;
grant create table to r2;
grant r2 to u1;

通过查询 select * from dba_role_privs where grantee='U1',发现角色r2已经付给了用户u1.