High US,HW enqueue wait event

Hi,

we have Oracle 9.2.0.8. Statpack shows that in certain time we have quite high enqueue waiting event ( around 20-30%). The detailed enqueue info from statpack:

Eq Requests Succ Gets Failed Gets Waits Time (ms) Time (s)
-- ------------ ------------ ----------- ----------- -------------

US       93,713       93,706           0       9,163
2,403.65       22,025
CI        5,000        4,996           0       1,133
11,477.73       13,004
HW      430,103      430,160           0       1,334
5,039.70        6,723
RO          382          384           0         230
4,938.91        1,136
TX      682,218      682,218           0       1,982
274.67          544
TM      319,346      319,343           3           9
22,090.11          199
SQ          254          254           0          17
1,087.76           18
CF        9,362        9,361           1          59
74.63            4

I know where the CI enqueue coming from (we have several drop tables jobs running in parallel). But Can somebody give hints about the US and HW enqueue? What might be the reason? I only know from the doc that HW is something to do with the segment space management operation and US is UNDO segment DDL.

Thanks,
Suri Received on Thu Feb 14 2008 - 13:42:09 CST