DBMS_Output: Some extra "enable" might be missing

Question

Sorry the silly question. I am stuck with Dbms_Output:

First I tried it within a batch/sqlplus call. But the spool file would only contain the message "pl/sql sucessfully executed". (See first code part)

I am running the code on Oracle Database 12c Enterprise Edition Release 12.1.0.2.0

Spool D:\log\spool.txt 
Declare
    Some_Num Number := 5;
Begin
    Dbms_Output.Enable(1000000);
    Dbms_Output.Put_Line('Id, Timestamp');
    For Rec In 
    (
        Select 1 As Id, Sysdate As Timestamp From Dual
        Union
        Select 2 As Id, Sysdate As Timestamp From Dual
        Union
        Select 3 As Id, Sysdate As Timestamp From Dual
        Union
        Select 4 As Id, Sysdate As Timestamp From Dual
    )
    Loop
        Dbms_Output.Put_Line( Rec.Id || ', ' ||  Rec.Timestamp );
        -- some code here was actually executed;
    End Loop;
    --Dbms_Output.Disable;
Exception
When Others Then
    Null;
    Dbms_Output.Put_Line('Error');
    --Dbms_Output.Disable;
End;
/
Spool Off
exit;

Answer 1

Found it myself. I needed to add

SET SERVEROUTPUT ON SIZE 1000000

at the beginning of the script.