Serial comm reading freeze

Hi guys!
I have a problem with a java program reading from a serial com port. I read sentences and handle some of them (!) in a database. Another application is querying the database. The problem is that the com port reading program freezes after some time (1day, 2 days...). It does not respond any more. Is it possible that there are to many incoming sentences filling the com buffer and freezing the com reading and database writing program? May this be due to slow database writing? What can be the cause?
The program restarts if any exception (com or database) is encountered.
Many many thanks for your help!
Best.

Also the serial ports are through ethernet converters or USB to serial converters.
It handles exceptions and closes the port when exception occurs.
Thanks.