-- 1. После такого,кажется, что с датами вообще не работает, но смотрим п.2
select cast(
          collect(sysdate) 
        as sys.odcidatelist) dt_table
from dual 
connect by level< 3 ;
-- 1.1. c over то же самое как с partition, так и  с order by
select cast(
          collect(sysdate) over(partition by level)
        as sys.odcidatelist) dt_table
from dual 
connect by level< 3 ;
-- 2. а вот тут забавно - убираем order by или весь over и все работает!
with calls as (
    select to_date('01.01.2011 10:00:00','dd.mm.yyyy hh24:mi:ss') dt,  20  duration,  30  cost,  1  a,  2  b from dual union all
    select to_date('01.01.2011 11:00:00','dd.mm.yyyy hh24:mi:ss'),  2 ,  4 ,  1 ,  2  from dual union all
    select to_date('01.01.2011 11:00:02','dd.mm.yyyy hh24:mi:ss'),  8 ,  8 ,  1 ,  2  from dual union all
    select to_date('01.01.2011 11:00:10','dd.mm.yyyy hh24:mi:ss'),  60 ,  0 ,  1 ,  2  from dual union all
    select to_date('01.01.2011 12:00:35','dd.mm.yyyy hh24:mi:ss'),  5 ,  0 ,  1 ,  2  from dual union all
    select to_date('01.01.2011 12:00:40','dd.mm.yyyy hh24:mi:ss'),  10 ,  10 ,  1 ,  2  from dual union all
    select to_date('01.01.2011 02:40:05','dd.mm.yyyy hh24:mi:ss'),  5 ,  0 ,  3 ,  2  from dual union all
    select to_date('01.01.2011 02:40:10','dd.mm.yyyy hh24:mi:ss'),  40 ,  23 ,  3 ,  2  from dual union all
    select to_date('01.01.2011 22:34:20','dd.mm.yyyy hh24:mi:ss'),  20 ,  6 ,  3 ,  2  from dual union all
    select to_date('01.01.2011 22:34:40','dd.mm.yyyy hh24:mi:ss'),  10 ,  0 ,  3 ,  2  from dual union all
    select to_date('01.01.2011 11:00:00','dd.mm.yyyy hh24:mi:ss'),  60 ,  0 ,  2 ,  1  from dual union all
    select to_date('01.01.2011 12:00:00','dd.mm.yyyy hh24:mi:ss'),  30 ,  10 ,  2 ,  1  from dual 
)
select 
    c.*,
    cast(collect(c.dt) over(partition by a,b order by dt) as sys.odcidatelist) dt_table
from calls c

create or replace type date_table_agg_type as object
(
   data  date_table,

   static function
        ODCIAggregateInitialize(sctx IN OUT date_table_agg_type )
        return number,

   member function
        ODCIAggregateIterate(self IN OUT date_table_agg_type ,
                             value IN date )
        return number,

   member function
        ODCIAggregateTerminate(self IN date_table_agg_type,
                               returnValue OUT  date_table,
                               flags IN number)
        return number,

   member function
        ODCIAggregateMerge(self IN OUT date_table_agg_type,
                           ctx2 IN date_table_agg_type)
        return number
)
/
create or replace type body date_table_agg_type
is

static function ODCIAggregateInitialize(sctx IN OUT date_table_agg_type)
return number
is
begin
    sctx := date_table_agg_type( date_table() );
    return ODCIConst.Success;
end;

member function ODCIAggregateIterate(self IN OUT date_table_agg_type,
                                     value IN date )
return number
is
begin
    self.data:=self.data multiset union all date_table(value);
    return ODCIConst.Success;
end;

member function ODCIAggregateTerminate(self IN date_table_agg_type,
                                       returnValue OUT date_table,
                                       flags IN number)
return number
is
begin
    returnValue := self.data;
    return ODCIConst.Success;
end;

member function ODCIAggregateMerge(self IN OUT date_table_agg_type,
                                   ctx2 IN date_table_agg_type)
return number
is
begin
    self.data:=self.data multiset union all ctx2.data;
    return ODCIConst.Success;
end;

end;

CREATE OR REPLACE FUNCTION date_table_agg(input date)
RETURN date_table
PARALLEL_ENABLE 
AGGREGATE USING date_table_agg_type;