declare
  cursor cur is
    select * from t
    for update;
  rec cur%rowtype;
  new_val date;
begin
  open cur;
  loop
    fetch cur into rec;
    exit when cur%notfound;
    
    new_val := sysdate;
    
    update t
    set    c2 = new_val
    where  current of cur;
    
  end loop;
  close cur;
end;
/

declare
  cursor cur is
    select * from t
    for update;
  type cur_tab is
    table of cur%rowtype
    index by pls_integer;

  recs cur_tab;
  dates dbms_sql.date_table;
begin
  open cur;
  loop
    fetch cur bulk collect into recs limit 100;
    exit when recs.count = 0;
    
    forall i in 1 .. recs.count     
      update t
      set    c2 = sysdate
      where  c1 = recs (i).c1
      returning c2
      bulk collect into dates;
    
  end loop;
  close cur;
end;
/