the physical map is used as often as the logical/symbolic one
every time You issue a "CICS SEND MAP" the data contained in the
logical/symbolic map ( which is just a piece of memory )
is merged with the data contained in the physical map and is
sent to the device
As per my knowledge, the Physical map is dummy. Its is used only for display purpose.. It cannot communicate with the terminal. So whenever there is a constant message or display, you can directly use the Physical map using EXEC CICS SEND command..
Where as inorder to communicate with terminal, this Physical map act's as a mediator b/w Symbolic map & terminal.. So when ever u required to use some dynamic (message or display) you need to use symbolic map