Without knowing more about your implementation I should say you need to create your own collection type. First check from the documentation what owa_util.ident_arr really is:
type ident_arr is table of varchar2(30) index by binary_integer;
What you need to do is then create your own collection with a table of varchar2:s greater then 30 as e.g.
type my_arr is table of varchar2(255) index by binary_integer;