Yea we use AS400/MAPICS for an ERP system. Windchill and AS400 are in no way tied together, even though I have had meetings about it and quotes made up stating what it would take to streamline everything. I am actually in IT and have been learning everything CAD as I go along while managing Windchill server and Creo installs.
Before Windchill, we were just using a regular File Server to store our CAD data on, but had to change since we now have remote sites. Everything was migrated in to Windchill and at the time, the migration team said most people just tie the File Name, Name, and Number together. So that is the direction we went and never thought any different.
Since this conversation started I've been talking with Engineering about trying to get this all tied together, but changing someone set in there ways is not that easy to do.