Evidently, a one time only procedure is a concept used in PL/SQL for initializing variables, an anonymous PL/SQL code block defined without an "END" statement.

A PL/SQL one-time-only procedure is an anonymous block of code encapsulated within a package. The one time procedure is executed only once when the package is invoked for the first time in a user session.

Here is an example of a one time only procedure in PL/SQL.  The end of a PL/SQL one time only procedure should be end of package body.  In the example of a one tike only stored procedure below, note that the one time procedure only has one END statement instead of two:

CREATE OR REPLACE PACKAGE
   package_name
AS
   FUNCTION  f_name ... ;
   PROCEDURE p_name ... ;
END package_name;
/

CREATE OR REPLACE PACKAGE BODY
   package_name
AS
FUNCTION  f_name...  BEGIN ... END f_name;
PROCEDURE p_name ... BEGIN ... END p_name;
BEGIN
-- whatever code is here executes one time only,
-- the first time the package is called
END package_name;
/

CREATE OR REPLACE PACKAGE pk_demo
AS
   PROCEDURE p_proc_1;

   FUNCTION f_func_1
      RETURN NUMBER;
END pk_demo;
/

CREATE OR REPLACE PACKAGE BODY pk_demo
IS
   a   NUMBER;

   FUNCTION f_func_1
      RETURN NUMBER
   AS
   BEGIN
      RETURN 10;
   END f_func_1;

   PROCEDURE p_proc_1
   IS
      li_num   NUMBER;
   BEGIN
      SELECT f_func_1
        INTO li_num
        FROM DUAL;

      DBMS_OUTPUT.put_line (li_num);
   END p_proc_1;
//one-time-only procedure defination
BEGIN
   DBMS_OUTPUT.put_line ('u r in the only block execution');
END pk_demo;
/
 
 
 
SQL>  execute pk_demo.p_proc_1;
you are in the only block execution
10

PL/SQL procedure successfully completed.

//here in the following the output is not same as earlier
SQL> execute pk_demo.p_proc_1;
10

PL/SQL procedure successfully completed.