What does that mean?
Davis-Monthan is an active base, with the 355th Fighter Wing being the host unit. There are a few tenant units, too. One of the tenant units is the 309th Aerospace Maintenance and Regeneration Group (AMARG), also known as The Boneyard.
http://www.dm.af.mil/Units/309AMARG.aspx
When I was stationed there over 20 years ago, they were only the AMARC (Center, instead of Group, I guess they've grown the mission a bit).