May be this query little bit help u solve sort activity problems:

COLUMN txt FORMAT A50 word
heading 'SQL text' justify left
COLUMN username FORMAT A20 heading 'User name' justify left
COLUMN sid FORMAT 9999 heading 'SID' justify right
COLUMN s# FORMAT 99999 heading 'Serial' justify right
COLUMN cur_cnt FORMAT 99999 heading '#|curs' justify right
COLUMN sort FORMAT 99999 heading 'Disk|sorts' justify right
COLUMN mem FORMAT 999G999G999 heading 'Total|memory' justify right
COLUMN exe FORMAT 999G999G999 heading 'Total|exec' justify right
COLUMN gets FORMAT 99999999 heading 'Blocks|get' justify right
COLUMN reads FORMAT 99999999 heading 'Blocks|read' justify right
COLUMN prows FORMAT 99999999 heading '#|rows' justify right
COLUMN hit FORMAT A24
heading 'Hit ratio' justify left

select
s.sid sid,
s.serial# s#,
s.username username,
a.sql_text txt,
count(c.sid) cur_cnt,
sum(sharable_mem)+sum(runtime_mem) mem,
sum(executions) exe ,
decode(sum(buffer_gets),0,'0',
ltrim(to_char(100-(sum(disk_reads)/(sum(disk_reads)+sum(buffer_gets))*100),'990D99'))||'% ('||
ltrim(to_char(sum(disk_reads),'99999999999'))||'/'||
ltrim(to_char(sum(buffer_gets),'999999999999'))||')') hit,
sum(sorts) sort,
sum(rows_processed) prows
from v$session s,
v$open_cursor c,
v$sqlarea a
where s.SQL_ADDRESS=c.ADDRESS(+) and
s.username is not null and
s.SQL_ADDRESS=a.ADDRESS and
s.username not in ('SYSTEM','SYS')
group by s.sid,
s.serial#,
s.username,
s.SQL_ADDRESS,
c.ADDRESS,
a.sql_text
order by 3,1;

COLUMN txt clear
COLUMN username clear
COLUMN sid clear
COLUMN s# clear
COLUMN cur_cnt clear
COLUMN sort clear
COLUMN mem clear
COLUMN exe clear
COLUMN gets clear
COLUMN reads clear
COLUMN prows clear
COLUMN hit clear