Who can resolve the error PLS-00201: identifier ... must be declared?

The above error occured when I tried to create and using function from package.
- I logged in with SYSTEM account
- created package and function of package as follow:

SQL> create package manage_emp as
2 procedure fire_emp(empid number);
3 end manage_emp;
4 create package body manage_emp as
5 procedure fire_emp(empid number) is
6 begin
7 delete from emp where id=empid;
8 end fire_emp;
9 end manage_emp;
10 .

and using the function fire_emp of the package by command:

SQL> execute manage_emp.fire_emp(2);

But SQL*Plus displayed the error:

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

Who can give me the solution to this problem?
Thanks,
Phuoc Nguyen Huu.

Use / to execute the CREATE statement, not ".". Because you ended the command with effectively an empty line, SQL*Plus ignored what you typed, and the PLS-201 was caused by the fact that the package didn't exist.

However if you do use / at the end, you'll get an error on the second CREATE, because those are two separate commands and each needs its own terminator.

IOW, you must do:

create or replace package manage_emp as
procedure fire_emp(empid number);
end manage_emp;
/
create or replace package body manage_emp as
procedure fire_emp(empid number) is
begin
delete from emp where empno=empid;
end fire_emp;
end manage_emp;
/

then you'll get:
SQL> execute manage_emp.fire_emp(2);
PL/SQL procedure successfully completed.

(Note I changed ID to EMPNO so it would work on my d/b).