Performance Tuning :: Update XML Eating Up A Lot Of Time

update xml eating up a lot of time is there any way to tune

SELECT UPDATEXML(:B3 , '/FCUBS_RES_ENV/FCUBS_BODY/FLD/FN[@TYPE="' || :B2 ||
'"]', :B1 )
FROM
DUAL

call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 0 0 0
Execute 499 0.44 0.90 0 3 0 0
Fetch 499 1.49 2.87 0 0 0 499
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 999 1.93 3.77 0 3 0 499

real code
SELECT updatexml(l_xml,
'/FCUBS_RES_ENV/FCUBS_BODY/FLD/FN[@TYPE="' ||
upper(replace(cspkes_misc.fn_getparam(p_parent_list,
l_parent_list_clob,
'Y',
l_cnt,
'>'),
'-',
'_')) || '"]/text()',
l_fn_str)
INTO l_xml
FROM dual;