cache size for restore with ArcServe6

Suddenly I can’t access anything below the VOL1, VOL2 or SYS level (or any other bacuped drives) when trying to restore. I can see all the backup sessions, the backup is working fine.
I find something on the net already it’s about increasing the CacheSize parameter in sys:\system\bti.cfg and unload and reload the btrieve.nlm and nwmkde.nlm (or restart the server). I’m still not 100% sure that the issues were the same and I don’t want to make experiences with the server in this moment.

What does btrieve.nlm and nwmkde.nlm ? And how can I unload and reload them without rebooting ?