use-id-pool in named.conf what does it do?

[V I V I D C I T I E S . c o m]

In my named.conf there is a line that reads

use-id-pool yes;

What does this mean?

I have searched dejanews, isc and excite.

I have DNS and Bind from Oreilly 3rd addition and there is not mention of it
there either.

Thanks
zack