Hi,
It all depends on whether your database freezes or the application. I don't think the database freezes, so at the time the freeze is occuring you can check outstanding thatnsaction with 'onstat -x'
'onstat -g sql' will give you an overview of all sessions.
You can check you message log for any errors on the database level.
onstat -p will show you the amount of lock wait, deadlocks, sequential scans etc.
All these could cause some sort of an application freeze. In that case, you might experience locking problems or index problems or database design problems.