in the A320 FCOM 3 (s.o.p) before takeoff : it says:
TCAS mode selector......................Select TA or TA/RA.
then it says :
the FAA recommends selecting TA in the following cases:
1-a known near by traffic that is in visual contact.
2-at particular airports and during particular procedures, identified by an operator as having a significant potential for unwanted or inappropriate RA (closely spaced runways,converging runways...)
Good Luck