ECAM will state Air Pack 1(2) Fault: Pack (affected) ....OFF and in Status you'll see Inop Sys: Pack 1(2)
after having referred to QRH,Computer Reset,C/B and having found nothing to deal with you definitely give a look to MEL. I'd be go minded, limiting FL315 according to fuel required and loaded, weather, kind of route and destination (obstacles,not assisted maintance places and so on)