Java Development Tools

i have read the following document..
http://otn.oracle.com/products/jdev/htdocs/bc4j/bc4j_temp_tables.html

and my query is..

I have 10 different application modules connected to database and they are inside a servlet contaienr and are singleton objects and are only dead when the servlet container is restarted or reloaded.
As ours is a multi-user application, the size of temporary tables is growing enormously day by day..
As adviced in the above document to make a database job to clean up these tables.
How about the data if it is used by application modules currently used by objects.
Is there any thing like working data -safe sort ..or it causes problems if i clean up the temporary tables for eg: PCOLL Persistence exceptions or if i try to delete when the tables are in use is it that the tables are not deleted...

if the tables are not deleted they r growing vastly and every time i have to stop my servlet server to do this and is mission critical..

please advice me..
regards
K°vi