we've got some performance problems and came up with the following:

drop table previous_events;

CREATE TABLE previous_events AS
SELECT SYSDATE timestamp, v$system_event.*
FROM v$system_event;

SELECT A.event,
A.total_waits - NVL (B.total_waits, 0) total_waits,
A.time_waited - NVL (B.time_waited, 0) time_waited
FROM v$system_event A, previous_events B
WHERE B.event (+) = A.event
AND A.event NOT IN
'client message', 'dispatcher timer', 'gcs for action',
'gcs remote message', 'ges remote message',
'lock manager wait for remote message',
'null event', 'Null event', 'parallel query dequeue', 'pipe get',
'PL/SQL lock timer', 'pmon timer', 'PX Deq Credit: need buffer',
'PX Deq Credit: send blkd', 'PX Deq: Execute Reply',
'PX Deq: Execution Msg', 'PX Deq: Signal ACK',
'PX Deq: Table Q Normal', 'PX Deque Wait', 'PX Idle Wait',
'queue messages', 'rdbms ipc message',
'smon timer', 'SQL*Net message to client',
'SQL*Net message from client', 'SQL*Net more data from client',
'virtual circuit status', 'wakeup time manager'
ORDER BY time_waited desc;

i/o slave wait 1059 6737
db file sequential read 1872 1445
db file scattered read 4081 1040

The create statement and the select are run within one minute. It seems our I/O slave is very high. Could someone tell me where to look for this?