[10.2.0.4 on W2K3] log file sync

Hi, I noticed a slow down of our database.
Looking at AWR report (one hour delay), the Top 5 Timed Events looks as follow

Event	Waits	Time(s)	Avg Wait(ms)	% Total Call Time	Wait Class
log file sync	42,162	6,665	158	88.6	Commit
log file parallel write	33,873	1,229	36	16.3	System I/O
db file parallel write	3,798	429	113	5.7	System I/O
db file sequential read	3,029	404	133	5.4	User I/O
control file parallel write	1,137	367	323	4.9	System I/O

 I read that it could be produced by multiple commits, so here are the following ratios :

user calls	1,426,574	393.38	51.55
user commits	26,839	7.40	0.97
user I/O wait time	70,263	19.38	2.54
user rollbacks	835	0.23	0.03

What do you think about ?

Rgds,