Is there a way I can eliminate this DFHAC2001 error message when I use the menu key to swap back and forth between the TPX menu and a live application?
The 'Menu' key is useful to swap between applications or 'return' to current application you are working with. Hitting the PA2 key twice, forces return to the application, which is working as designed.
This sequence can be changed if its required that pressing the PA2 key twice, is restricted.
Set reserved option 57 in the SMRT under option 13. In order to get to option 57, the extended option menu can be reached by entering 'Options' in panelid TEN0099.
With this set, if the menu key is entered from the TPX menu "nothing happens". The user stays at the TPX menu. You must now force the user, at the TPX menu. to hit enter with the cursor on the session line to get back to the session / application.
The other method to restrict this would be to code a TPXUCMND exit, using call point 4 to check for the PA2 key being entered from the TPX menu. Discard the PA2 and issue a $COMMAND macro to Activate the "remembered" session.