How to display current session parameter value

Question

Hi,
How can a db user know value of a session parameter, if he doen't have privilege to access v$parameter?
SQL> conn hr/hr
Connected.
SQL> show parameter QUERY_REWRITE_ENABLED
ORA-00942: table or view does not exist
SQL> alter session set QUERY_REWRITE_ENABLED=true ;
Session altered.
-- how can the user HR know the value of QUERY_REWRITE_ENABLED

Answer 1

You can code a PL/SQL function and grant only execute privilege to the user:
SQL> select * from v$version;
BANNER
Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production
PL/SQL Release 11.1.0.6.0 - Production
CORE    11.1.0.6.0      Production
TNS for 32-bit Windows: Version 11.1.0.6.0 - Production
NLSRTL Version 11.1.0.6.0 - Production
SQL> drop user admin cascade;
User dropped.
SQL> create user admin identified by admin;
User created.
SQL> grant create session, create procedure to admin;
Grant succeeded.
SQL> grant select on sys.v_$parameter to admin;
Grant succeeded.
SQL> connect admin/admin
Connected.
SQL> show user;
USER is "ADMIN"
SQL> create or replace function get_parm (p_pn in varchar2) return varchar2
  2  as
  3  l_val v$parameter.value%type;
  4  begin
  5   if ( UPPER(p_pn) = 'QUERY_REWRITE_ENABLED' )
  6   then
  7        execute immediate 'select value from v$parameter where name = :1 '
  8        into l_val using p_pn;
  9        return l_val;
10   else
11      raise_application_error(-20000,'Invalid parameter');
12      return null;
13   end if;
14  end;
15  /
Function created.
SQL> grant execute on get_parm to test;
Grant succeeded.
SQL> connect test/test
Connected.
SQL> show parameter query
ORA-00942: table or view does not exist
SQL> select admin.get_parm('query_rewrite_enabled') from dual;
ADMIN.GET_PARM('QUERY_REWRITE_ENABLED')
TRUE
SQL> select admin.get_parm('compatible') from dual;
select admin.get_parm('compatible') from dual
ERROR at line 1:
ORA-20000: Invalid parameter
ORA-06512: at "ADMIN.GET_PARM", line 11