question on v$system_event

I have question about stats from v$system_event. i just checked on one of db

SELECT EVENT,AVERAGE_WAIT
FROM V$SYSTEM_EVENT
WHERE EVENT LIKE 'db file s%';

EVENT AVERAGE_WAIT
db file sequential read 1159.27
db file scattered read .15

are these stats okay ?
table scans are cheaper v/s index scan or i am reading it wrong

thanks gc

not enough to say anything

you need to get delta values, not values since instance was brought up (which is what v$system_event shows)

I have statspack running.

just queried the statspack table.

SNAP_ID EVENT TOTAL_WAITS
856 db file scattered read 18367608
856 db file sequential read 15646602
857 db file scattered read 18367635
857 db file sequential read 15668088
858 db file scattered read 18367705
858 db file sequential read 15793211
859 db file scattered read 18367739
859 db file sequential read 16854095


i checked with writer of

http://www.evdbt.com/SearchIntelligenceCBO.doc ( Very GOOD Article )

since async io is turned on ! the stats i am seeing might be wrong

any other thoughts
thanks