SQL>create table tab1(col1 number,col2 varchar2(20))
    initrans 1 maxtrans 1
SQL> /

Table created.

SQL> declare
  2  i number;
  3  begin
  4  for i in 1..10000 loop
  5  insert into tab1 values(i,'value');
  6  end loop;
  7  commit;
  8  end;
  9  /

PL/SQL procedure successfully completed.

SQL> update tab1 set col2='updated' where col1=1;

1 row updated.

Session 2:

SQL> update tab1 set col2='updated' where col1=2;

1 row updated.