Explanation of ntds log files

I’m looking for an explanation of, or directions to where I can find, detailed information regarding ntds log files. I understand they are the AD transaction log(s). My recently installed Win2k Server seems to be collecting these rather large files(10.2Mb) to the point of running out of disk space. I’ve read how to move them using ntdsutil.

Can they be purged? What is the “standard” length of time these logs should be retained before purging ? Are there ways to limit the number of log files that are retained?
Thanks in advance !