step by step progress logging for oracle plsql

I'm having a message_log table with ID, Severity Level, Message, Log Date & Time.

I'm using below procedure to insert log messages to log table in my PL/SQL scripts.

add_log(ID,'START','DEBUG','No CDR Detail to be processed', sysdate);    

But in case of failure I see some message are not getting logged. What is the best method to log step by step progress of a plsql progress (until failure point if needed)?

create or replace procedure add_log 
        (stp varchar2, code varchar2, log_message varchar2, logdat date)
    is 

begin

    insert into message_log 
    (SEQ,PROC_STEP,
    CODE,
    LOG_MESSAGE,
    LOG_DATE
    )
    values 
    (log_SEQ.NEXTVAL,stp,code,log_message,logdat)
    ;

end;