I don’t know HFA, but sopme third-party packeges create work files in QTEMP and/or other libraries that are deleted at EOJ and/or when the user signs off. Also, some apps open a bunch of files at sign-on time. If you do a WRKSYSSTS and the DASD usage is high, this may be a problem. Also, take a look at the following: (1) large reports that are in OUTQs, (2) reduce the time that system logs are kept on the system, (3) permanently apply all PTFs, and (4) change system value QRCLSPLSTG to a value ‘1’. Also, if library QRPLOBJ has a lot of objects in it, you may want to clear it. This library is used to archive objects that get re-compiled; it is cleared automatically at IPL. GOOD LUCK!
Note that clearing QRPLOBJ <i>is not</i> good advice as a general statement. Deleting everything that you recognize out of QRPLOBJ is okay (as long as the objects are not in use), but the system itself may move objects to QRPLOBJ as part of its own processes. You almost certainly do not want to accidentally delete one of those objects.