SQL> create table mini ( id integer not null primary key, value varchar2( 100 ), 
  2      locked char( 1 ) default 'N' check ( locked in ( 'Y', 'N' ))) ;

Table created

SQL> create sequence mini_seq ;

Sequence created

SQL> create function insert_mini ( p_value varchar2 ) return integer is
   2     result integer ;
   3   begin
   4     insert into mini ( id, value, locked )
   5       values ( mini_seq.nextval, p_value, default ) 
   6       returning id into result ;
   7     return result ;
   8   end ;
   9   /

Function created

SQL> create procedure update_mini ( p_id integer, p_newvalue varchar2, p_newlocked char ) is
   2   begin
   3     update mini set
   4       value = p_newvalue,
   5       locked = p_newlocked
   6     where id = p_id ;
   7   end ;
   8   /

Procedure created

SQL> create procedure delete_mini ( p_id integer ) is
   2   begin
   3     delete from mini where id = p_id ;
   4     if sql%rowcount <>  1  then raise_application_error ( - 20100 , 'Something wrong with delete' ) ; end if ;
   5   end ;
   6   /

Procedure created

SQL> create trigger mini_bd before delete on mini for each row
   2   begin
   3     if :old.locked = 'Y' then 
   4       raise_application_error ( - 20101 , 'Record ' || :old.id || ' is locked and cannot be deleted' ) ;
   5     end if ;
   6   end ;
   7   /

Trigger created

SQL> var new_id number ;

SQL> begin :new_id := insert_mini ( 'Первая запись' ) ; end ;
   2   /

PL/SQL procedure successfully completed

new_id
---------
 1 

SQL> begin :new_id := insert_mini ( 'Вторая запись' ) ; end ;
   2   /

PL/SQL procedure successfully completed

new_id
---------
 2 

SQL> begin :new_id := insert_mini ( 'Третья запись' ) ; end ;
   2   /

PL/SQL procedure successfully completed

new_id
---------
 3 

SQL> begin update_mini ( p_id =>  2 , p_newvalue => 'Обновленная вторая запись', p_newlocked => 'Y' ) ; end ;
   2   /

PL/SQL procedure successfully completed

SQL> begin delete_mini (  1  ) ; end ;
   2   /

PL/SQL procedure successfully completed

SQL> select * from mini ;

                                     ID VALUE                                                                            LOCKED
--------------------------------------- -------------------------------------------------------------------------------- ------
                                       2  Обновленная вторая запись                                                        Y
                                       3  Третья запись                                                                    N

SQL> begin delete_mini (  2  ) ; end ;
   2   /

ORA- 20101 : Record  2  is locked and cannot be deleted
ORA- 06512 : at "TEST.MINI_BD", line  3 
ORA- 04088 : error during execution of trigger 'TEST.MINI_BD'
ORA- 06512 : at "TEST.DELETE_MINI", line  3 
ORA- 06512 : at line  1 

SQL> begin delete_mini (  10  ) ; end ;
   2   /

ORA- 20100 : Something wrong with delete
ORA- 06512 : at "TEST.DELETE_MINI", line  4 
ORA- 06512 : at line  1