two questions regarding default audit behavior

I have two questions regarding default audit behavior (i.e. auditd is running, but there is nothing in audit.rules but "-D" and "-b 256"): 1) what is being audited? 2) can I use the -D command to prevent those things from being audited? I am required to have auditing running, but what I need to audit is specific. One server in particular is slow (a 750 MHz Pentium III) to start with, and default auditing is slowing it down to a crawl. Bill Tangren