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Proxy users [Oracle]

connect / as sysdba
A proxy user ...
create user          proxy_user
identified by        pw_proxy
default tablespace   users
temporary tablespace temp;
... and a target user is created.
create user          target_user
identified by        pw_target
default tablespace   users
temporary tablespace temp
quota unlimited on   users;
The target user is altered (so to truly make him a target user through which a proxy user can connect).
alter user target_user grant connect through proxy_user;
The create session and the create table system privilege is granted.
grant create session,
      create table
to    target_user;
Note: only the target user has the connect session privilege, not, however, the proxy user!
connect target_user/pw_target
The target user creates a table, but does not grant select on it to the proxy user:
create table targets_table (
  col  varchar2(10)
);
Insert something...
insert into targets_table values ('foo');
The proxy user can now connect with the proxy_user[target_user] syntax, hence becoming the target user.
connect proxy_user[target_user]/pw_proxy
Indeed, the table can be selected from:
select * from targets_table;
COL
----------
foo