To know more about Procedures in pl/sql ,let us first start with the basic requirement of procedures in pl/sql.

Procedures are a type of schema object which can be stored in a database.
Procedures are a type of subprogram that perform a particular action.
Promotes maintanability and reusability.

syntax to create procedure:-

create[OR Replace] Procedure Procedure_name
[parameter1] datatype1
[parameter2]datattype2

Is/As

[local variable declaration;...]
begin

action

end [Procedure_name];


use the Create clause to create the Standalone Procedure that is stored in the Oracle Database

Use the Replace clause to replace the already existing Procedure name with the name you want to display the procedure with.

let us take the example for increase salary

Code Listing 1: increase_salary procedure with FOR loop

PROCEDURE increase_salary (
   department_id_in   IN employees.department_id%TYPE,
   increase_pct_in    IN NUMBER)
IS
BEGIN
   FOR employee_rec
      IN (SELECT employee_id
            FROM employees
           WHERE department_id =
                    increase_salary.department_id_in)
   LOOP
      UPDATE employees emp
         SET emp.salary = emp.salary + 
             emp.salary * increase_salary.increase_pct_in
       WHERE emp.employee_id = employee_rec.employee_id;
   END LOOP;
END increase_salary;

Suppose there are 100 employees in department 15. When I execute this block, 
BEGIN increase_salary (15, .10); 
END; 

the PL/SQL engine will “switch” over to the SQL engine 100 times, once for each row being updated. Tom Kyte, of AskTom (asktom.oracle.com), refers to row-by-row switching like this as “slow-by-slow processing,” and it is definitely something to be avoided.