You're not the first to ask this question. We have a knowledge base article on this:

http://www.nessoft.com/kb/20

If you have questions/concerns after reading that, please let us know.

Oh - here's a discussion on this:

http://www.nessoft.com/forums/showflat.php?Number=655

There are a couple of others as well, but this is a good one talking about reasons why it behaves like this.

- Pete