There is no such thing as "Preserving RAM".  RAM is the physical memory used by the PC and if efficient the PC should use 100% of it unless there is no call to use all of it.  When RAM is full Windows then uses the Swap Files on disk as virtual memory.  30 minutes of music processing will use up all but the largest amount of RAM and even then will very likely use up that and hence slow down processing.  Don't be tempted to free up RAM with RAM cleaner utilities, they are a waste of time IMHO as you want to utilize the maximum amount of RAM for efficiency.
Sorry if this is not what you want, but, your question is very vague
----- Original Message -----
From: Brandon Hull
Sent: Sunday, May 29, 2005 4:29 AM
Subject: [Audacity-users] RAM

As someone new to Audacity, does anyone know any workarounds for preserving RAM? I've got recordings about 30 minutes in mind...

Thanks in advance,