parallel query and latch waits

I have a table set up with parallel degree 4 the table is spread out across 4 physical disk mounts.

Everything run great except if I have a subquery  

i.e.

select sum(impressions)
from fact_table --parallel degree 4
where user_id in (select user_id

                   from users 
                   where  external_role_type IN('Named User', 'Registered User')
                 )

latch waits are 60% of non-idle wait time (from spotlight) What can I do to reduce this latch problem?

If I remove parallel from the fact table I do not have a problem with latches?

Thanks Rob Received on Thu Jun 07 2001 - 14:06:38 CDT