Try using the 11g parameters, add/change or remove the following:
Code:
db_cache_size				#<= Remove
db_writer_processes			1
disk_asynch_io				TRUE
filesystemio_options 			SETALL
memory_max_target			2400M  #<= Max memory...
memory_target				2000M  #<= SGA 1G + PGA 0.5G + Extra
pga_aggregate_target			#<= Remove
sga_max_size                            #<= Remove
shared_pool_size                        #<= Remove
sort_area_retained_size                 #<= Remove
sort_area_size                          #<= Remove

PS: Allocate as much memory as possible.
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