SQL> show user 
USER is "TARUN"

SQL> create procedure check1( n1 number) as
  2  begin
  3  dbms_output.put_line(n1);
  4  end;
  5  /
Procedure created.

SQL> set serveroutput on;
SQL> exec check1(3)
3

PL/SQL procedure successfully completed.

SQL> show user
USER is "SCOTT"

SQL> exec tarun.check1(3);
BEGIN tarun.check1(3); END;

      *
ERROR at line 1:
ORA-06550: line 1, column 7:
PLS-00201: identifier 'TARUN.CHECK1' must be declared
ORA-06550: line 1, column 7:
PL/SQL: Statement ignored


SQL> show user 
USER is "TARUN"

SQL> grant execute on check1 to scott;

Grant succeeded.


SQL> show user
USER is "SCOTT"

SQL> exec tarun.check1(4);
 4

------And now i am creating a procedure in scott's schema with --------the same name

SQL> create procedure check1 as
  2  begin
  3  dbms_output.put_line('hello');
  4  end;
  5  /

Procedure created.

SQL> exec check1;
hello

PL/SQL procedure successfully completed.

SQL> exec tarun.check1(5);
5

PL/SQL procedure successfully completed.

SQL> select * from session_privs;

PRIVILEGE
----------------------------------------
CREATE SESSION
ALTER SESSION
UNLIMITED TABLESPACE
CREATE TABLE
CREATE CLUSTER
CREATE SYNONYM
CREATE VIEW
CREATE SEQUENCE
CREATE DATABASE LINK
CREATE PROCEDURE
CREATE TRIGGER

PRIVILEGE
----------------------------------------
CREATE TYPE
CREATE OPERATOR
CREATE INDEXTYPE

14 rows selected.