v$active_session_history output issue

 Hi,

Please check the below query. Why it is not providing the name of event it was waited for 30658680 seconds. Kindly suggest if query need to be change.

SQL> select event,

sum(wait_time +

time_waited) total_wait_time

from v$active_session_history

where sample_time between

sysdate  - 30/2880 and sysdate

group by event

order by total_wait_time desc;  2    3    4    5    6    7    8

EVENT                               TOTAL_WAIT_TIME

----------------------------------- ---------------

                                           30658680

db file sequential read                    10167978

SQL*Net more data to client                 2421787

db file parallel read                        840006

db file scattered read                       789010

db file parallel write                       207854

log file parallel write                       60361

os thread startup                             25680

control file sequential read                   6140