How to force Fusion to purge every rendered frame?

I'm sure I've seen somewhere before this description where to enter what to enter in the console, but can not find anywhere now.
there were several options how to do this, and the article stood for that in several occasions it makes fusion render faster when ram is purged....
I certainly noticed this too when almost all of memory is used fusion drops rendering frames dramatically... the first 100 frames rendered in 30 sec and the next 200 are rendered in 5 minutes giving me the overall render time up to 6 minutes.
So I'm looking for the ways to optimize it via the settings, not buying an additional ram so to speak...

or every tenth frame?

http://www.steakunderwater.com/wesuckle ... 5684#p5684

Thanks! but I've seen some more documentation and different approaches to this like there were discussed 3 ways to do this...

And do I need to rename it to .lua or .fuscript?

and how is to revert this to normal?