As far as I know, which is somewhat limited, there is no global user auditing system. BUT, there are processws to track any and all address book changes. If you look at the processing option for the address book app (P01012) you will see under the versions tab/option 1, the ability to activate the audit trail. This is also available for the Customer master as well.
As for the rest of JDE, I am not sure. I also wish I knew.