Well, here is a quick one-liner to get the available memory on an AIX system, with an detailed listing of each size of each memory DIMM on currently installed banks (provided in MB):

# lscfg -vp | egrep 'Memory DIMM|Size'
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048
     Memory DIMM:
       Size........................2048