Does DBA create log files, i.e. which user made what change when?  If so, where are they normally located?

The reason it does not is that the Tp5wdba.exe engine which ultimately controls the security, is not persistent.
 
It reads the user login when you sign in, assigns appropriate security based on the security grid file and the BKMENU.ARY file and then stops.  Dead.
 
After the initial validation, the DBA engine has no clue who is logged in.
 
Since it has no clue who is logged in, there is no way to keep track of activities by user.